# How to figure how much oil for mold.



## Soapmaker Man

Hi everyone.I wanted to post this as a sticky so all could learn how much oils are needed for your mold.  Here is the way to figure it.

Lets use a log mold that is 12 inches long, 3-1/2 inches wide, and you want to pour to a depth of 2-1/2 inches.

You take length X width X height of pour, that number X .40.  So;

12 X
3.5=
42

42X
2.5=
105

105X
.40=
*42 ounces of oils needed for this mold.*

Apply these same numbers for your mold size, weather a log, slab, or block. :wink: 

Paul


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## jadiebugs1

Thanks Paul!


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## IanT

hey paul, thanks for the helpful thread!!..


just curious, where does the .40 come from??


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## Tabitha

MELT & POUR

I thought I would add how to figure hw much M&P for a mold. It's SUPER easy!

1) Fill your mold w/ water.
2) Pour the water into a measuring cup & measure.
3) That is how much _melted_ M&P soap it will take to fill your mold.


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## Soapmaker Man

IanT said:
			
		

> hey paul, thanks for the helpful thread!!..
> 
> 
> just curious, where does the .40 come from??



Something I learned by asking questions at another forum years ago.    I am not the one who figured this out, can't take credit for it. I can 101% absolutely guarantee this to work!  I have been using this calculation for all my TOG Molds since I started making them, and it always works perfectly! 8) 

Paul


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## IanT

Im going to do some more research but i do trust you that it works! i just like to know the logistics behind everything (again just my personality  ! Thanks!

Im going to have to try this...get a big mold and just do it up


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## Soapmaker Man

IanT said:
			
		

> Im going to do some more research but i do trust you that it works! i just like to know the logistics behind everything (again just my personality  ! Thanks!
> 
> Im going to have to try this...get a big mold and just do it up



Tell you what Ian, in front of everyone, if it doesn't work, I'll send you a new TOG Mold, FREE!  How is that for confidence buddy?


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## IanT

hahaha works for me!! I trust your word though! never led me astray yet through the what...million and a half questions ive asked and youve answered so far!??


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## CiCi

What if your mold is round or odd shaped?


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## MetalSubstance

Basically, you simply multiply the volume of the mold by .40, regardless of the shape of the mold.

So, if the mold is cylindrical with the base radius of r and height of h, the formula would be: pi * r * r * h * .40, or about 1.257 * r * r * h.

If the mold is a half-sphere or a dome with radius r, the formula is: 2/3 * pi * r * r * r * .40, or about 0.829 * r * r * r.

Hopefully the math wasn't too confusing.  Perhaps someone can explain it better than I can.

--Metal Substance

P.S. -- one way to figure out the volume of the mold is to fill it all the way with water, then pour the water into a measuring cup.  Then, simply multiply the amount of water in the cup with .40 to get the amount of oil to use.


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## Sholdy

MetalSubstance said:
			
		

> P.S. -- one way to figure out the volume of the mold is to fill it all the way with water, then pour the water into a measuring cup.  Then, simply multiply the amount of water in the cup with .40 to get the amount of oil to use.



LoL    That way seems the best.    

p.s.    The value of pi is 3.14, so the formula for a cylinder (round mold) is 
3.14 x r x r x h
where,
r = radius
h = height

Heck, I'm going the water method.   :?


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## Missjulesdid

Thank you so much for helping with the volume of a cylinder... I seem to have blocked out 10th grade completely!


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## IanT

Im so horrible at math its not even funny....I had to study soooooo long and hard to pass those classes in school, came out o.k. thanks to the math labs and such but it was HARD


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## jones10021

Thank you Paul.  It was extremely helpful.  I desperately needed to find out how much oil to use in the mold and then I stumbled upon your thread. Your calculations were very clear and helpful.  I'm positive my soap turns out great.

Good to know that.
Thanks you all.


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## busymammaof3

Great information to have! BTW...I have one of Paul's latest molds and he is right on with his calculations! I love it so much...I rarely want to use the small, 4 cavity soap molds from the craft store now. They have pretty designs...but Paul's mold is so much easier to use! I've made half a dozen or so batches with it, so far, Paul! Lovin' every minute of it!


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## heart of dixie soap co

*oil for molds*

you are correct. depending on the size of your molds, i have found this to be accurate within an ounce or two.  just upgraded from 4# molds to  7# molds.  it was right on the money.

lather up!

monet


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## millyb60

*..*

Just one question .. when the M&P base is in blocks, how do you know how much to melt to get the "liquid amount"? I hope that makes sense.. for example, say my mould held 100ml of water, how much solid block soap do i need to weigh out in order to have 100ml of melted soap? One would assume around 100g, but i dont know...

That may have a really easy and "commonsense" answer, but times when i've used this method, ie measuring how much water the mould can hold, i've not been totally successful, had a bit too much most of time.. 

Thanks very much everyone  would really appreciate an answer for this


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## soaper41

Thank you for that Paul.
Here riding out tropical storm Fay.
Up listening to the wind battering on our windows.
 8)


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## eargirly

I like to know the reasons behind things to.  Is it because the amt of oils used in the process equals 40% of the total volume of the final outcome?  That would be the only reason I can figure for the .40 there.  

Hope someone can help me on that.  I haven't done this stuff yet, so I am a complete noob.  But, first batch is coming soon and I want to be sure I have all this right.    I studies and studied the RTCP method last night and lye calculators this morning.  

Thanks for any help!~
ear


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## lindar

great information to no would have liked to have seen this a few months ago


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## Bigmoose

Hello everyone,

I make my own molds and use a volume calculater at the site below.


Hope this helps everyone as much as it has helped me.

Bruce

[Edited by SMF Modmin Team to remove non-functioning link]


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## ballininthamix

eargirly said:
			
		

> I like to know the reasons behind things to.  Is it because the amt of oils used in the process equals 40% of the total volume of the final outcome?  That would be the only reason I can figure for the .40 there.



I think it is important to note that the formula Paul provided gives you the total *weight* in ounces of oil by multiplying the total *volume* in cubic inches by .40. This doesn't necessarily mean that the oils make up 40% of the volume. So this formula will work as long as you can compute the volume of your mold in cubic inches.

Now let's say you have an odd shaped mold or want to measure the volume in fluid ounces. You can still use this method, just make sure you convert your liquid ounces to cubic inches.

There are approximately .554 fluid ounces in a cubic inch. So multiply your total fluid ounces by .554 and multiply that by .40 and you've got your total weight of oil. Like this:

TOTAL (fl oz.) x .554 x .40 = TOTAL OIL (oz.)


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## eargirly

thanks for that info bigmoose and ballin!  That helps me a great deal as well!  I am having my father (a woodworker) make some molds for me and that is great info, indeed.  Everyone here is so helpful.  Thank you over and over again!

~ear


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## welder

ballininthamix said:
			
		

> eargirly said:
> 
> 
> 
> 
> I like to know the reasons behind things to.  Is it because the amt of oils used in the process equals 40% of the total volume of the final outcome?  That would be the only reason I can figure for the .40 there.
> 
> 
> 
> 
> I think it is important to note that the formula Paul provided gives you the total *weight* in ounces of oil by multiplying the total *volume* in cubic inches by .40. This doesn't necessarily mean that the oils make up 40% of the volume. So this formula will work as long as you can compute the volume of your mold in cubic inches.
> 
> Now let's say you have an odd shaped mold or want to measure the volume in fluid ounces. You can still use this method, just make sure you convert your liquid ounces to cubic inches.
> 
> There are approximately .554 fluid ounces in a cubic inch. So multiply your total fluid ounces by .554 and multiply that by .40 and you've got your total weight of oil. Like this:
> 
> TOTAL (fl oz.) x .554 x .40 = TOTAL OIL (oz.)
Click to expand...




Good point Ballin.

Until you mentioned that, like Eargirly, I had also mistakenly thought that 0.40 was the volume of oil required (as in 40% of total volume)

Okay, so once I know my mold volume and do the math to get the oil weight in ounces, how do I calculate how much water I need?

I know that after I calculate my oil requirement (in ounces), I simply run that figure through a lye calculator to find the lye measure required, but  I still don't know how to get the water measure required.

Help!!!!!


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## donnux

*Calculating mold size*

I just set up a bunch of soap making URLs and was looking for an answer to exactly this question. So I came to The Soap Making Forum site and found that it is the second question!

I arrived at this 0.4 number a different way, that is by measuring several bars of soap, then averaging their weights. Some simple arithmetic worked out to 0.4 ounces per cubic inch of soap, the same number you have come up with. So now I can consider that I did some math right, for a change!

Thanks for verifying this for me, now I can proceed with more confidence that my goop will fit into the mold without overflowing.


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## maheka

Soapmaker Man said:
			
		

> Hi everyone.I wanted to post this as a sticky so all could learn how much oils are needed for your mold.  Here is the way to figure it.
> 
> Lets use a log mold that is 12 inches long, 3-1/2 inches wide, and you want to pour to a depth of 2-1/2 inches.
> 
> You take length X width X height of pour, that number X .40.  So;
> 
> 12 X
> 3.5=
> 42
> 
> 42X
> 2.5=
> 105
> 
> 105X
> .40=
> *42 ounces of oils needed for this mold.*
> 
> Apply these same numbers for your mold size, weather a log, slab, or block. :wink:
> 
> Paul


Anyone would like to convert this to the metric system? My math isn't enough...


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## Godiva

Missjulesdid said:
			
		

> Thank you so much for helping with the volume of a cylinder... I seem to have blocked out 10th grade completely!



I homeschool my son, who is in 8th grade, and had to learn the formulas for volume.  I LOVED math in school, was my favorite subject.  Science was my second favorite.  Then English.  Did not like history much.  My hubby hated math.  Luckily all my kids inherited my propensity for math and have done well.  My 3 oldest have told me that other kids in their class would seek them out for help.  

Now that I'm going thru American History with my son, I find I enjoy it more this time around.


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## JulieJ

What about the lye/water solution?  Don't you have to figure that addition to the volume of the mold?  [email protected]


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## Godiva

JulieJ said:
			
		

> What about the lye/water solution?  Don't you have to figure that addition to the volume of the mold?  [email protected]



I use a soap calculator and it will calculate how much water/lye to use.  I've been using Paul's formula for all the different boxes I've been using, and it has worked out perfectly.  

So (L x W x H) x .40 = amount of oils.  If it's 3 lbs (48 oz), you enter the percentage of each oil, hit compute, and it will tell you how much water and lye you need for your recipe.


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## JulieJ

Oops, I guess I didn't make my question clear, sorry.  What I meant to ask is if you have to figure in the lye/water solution into the volume.  For example... if your mold holds 16 ounces  and your recipe calls for 16 ounces of oils, PLUS 6 ounces of water/lye solution, wouldn't you need a mold that holds 22 ounces? Thank you.


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## Godiva

JulieJ said:
			
		

> Oops, I guess I didn't make my question clear, sorry.  What I meant to ask is if you have to figure in the lye/water solution into the volume.  For example... if your mold holds 16 ounces  and your recipe calls for 16 ounces of oils, PLUS 6 ounces of water/lye solution, wouldn't you need a mold that holds 22 ounces? Thank you.



I suppose so.  If I am using a recipe that uses ounces instead of percentage of the oils, I will add up the oils and then figure out what percentage each oil is in the recipe, and apply those percentages to however many ounces I need for my mold.  I've not worked the other way around.


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## Val

Hi

I found this and It helped me on the mold size and how much. You just enter the measurements of your mold and it give you how much oils to use.

Hope this helps,

Val

[Edited by SMF Modmin Team to remove non-functioning link]


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## xraygrl

I just made new molds today (with DH's help....he would NOT let me play with the saw  :evil: ) so I needed this. TFS!


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## topcat

I tried using this formula to calculate in grams oils weight and it does not compute  :wink: 

I found this link online which give the metric calculation for those of us who use grams. I am just about to make a batch in a new mould using this calc so I will edit my post and let you know how successful it is.

Tanya 

*Edited to add: *Yes - this metric calculation definitely worked for my new mould. Excellent!

[Edited by SMF Modmin Team to remove non-functioning link]


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## chrisnkelley

Thanks for the formula!  Seems pretty simple!  So, by oil, you mean the combo of bases you are using, right?  (I'm new, sorry!) Like olive oil, castor oil, etc?


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## topcat

Yes, oil weight is the total weight of all the oils you plan to use in your recipe.  HTH!

Tanya


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## chrisnkelley

Thanks!  It doesn't include weight of essential oils or additives though, right?


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## Christianbeauty

This is way too helpfu--i have been racking my brain for days trying to figure it out and I figure I would just pour all my oils in the mold and divide it in half to see if it works--but doing this formula is way too helpful---i am going to try it in my new mold and thanks!!


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## heartsong

*x*

hi there!   

there is an auto-calculator at www.soapersmarker.com

this does both square and round molds.

these are all based on a no water discount-if you use a water discount, you may need to add a little extra oil, depending on the size of your molds.


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## Guest

I did soap maker mans calculation for my box. Guess what??? It was exactly right. This is only my second batch of CP, thank you so much soap maker man. You rock!!!!


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## Soapmaker Man

bconrade884 said:
			
		

> I did soap maker mans calculation for my box. Guess what??? It was exactly right. This is only my second batch of CP, thank you so much soap maker man. You rock!!!!



You're quite welcome.  

SMM :wink:


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## Bnky

I just got a small mold for sample bars and this is just what I needed.  I wish I had looked at it before I made my large batches.  Great info, Thanks Paul!
Bnky


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## kslo78

I just bought a silicon mold for $3 at Marshalls and this post was super helpful.  It's a 2.3 lb loaf mold.


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## Guest

I hope someone can answer this question. I'm going to make some soap tonight and plan to mix shredded soap pieces into it before molding. This would obviously increase the volume of the batch. 
How can I account for this extra soap and figure out what size mold to use?


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## cwayneu

juicybath said:
			
		

> I hope someone can answer this question. I'm going to make some soap tonight and plan to mix shredded soap pieces into it before molding. This would obviously increase the volume of the batch.
> How can I account for this extra soap and figure out what size mold to use?



First off, you need to know the total batch size by finding the mold volume and multiply by .4, as this thread explained. For example, let's say you have a slab mold 10" by 10 1/2", and you pour your bars 1" thick. 

You take (L X W X H)

10 X 10.5 X 1 = 105, then 105 X .40 =42 oz  So your total batch size is 42 oz. 

However, since you are replacing some of the batch total with already made soap (your shreds), you need to reduce the batch total by the amount of shreds you are adding. The percentage of shreds is actually your choice, but we have found that 20% is just right for us. Whatever number you pick, the next step is to determine ounces of the shreds part and the batter part.

Following on with the 42 oz batch example, we want 20% shreds and 80% new batter.

Shreds = 42 X 20% ( or .2 ) = 8.4 oz
Batter   = 42 X 80% ( or .8 ) = 33.6 oz

So you need to weigh out 8.4 oz of shreds, and use 33.6 oz as your batch size in soapcalc to figure out your oils, lye, etc.

Then you make your 33.6 oz batch as normal, but just before you pour into the mold you stir in your 8.4 oz of shreds.

Hope this helps.


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## Soaps House

All you have to do is find the area out and then multiply it by .4. It doesn't matter is the mold is square, round, or a triangle. Unfortunately I don't remember the formulas for round or triangle, but that is why we have Google right?

John


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## cwayneu

Soaps House said:
			
		

> All you have to do is find the area out and then multiply it by .4. It doesn't matter is the mold is square, round, or a triangle. Unfortunately I don't remember the formulas for round or triangle, but that is why we have Google right?
> 
> John



It's actually .4 times the mold volume (in cubic inches), not just the area (square inches) to get the batch size in ounces.


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## Soaps House

cwayneu said:
			
		

> It's actually .4 times the mold volume (in cubic inches), not just the area (square inches) to get the batch size in ounces.



Your right...just a little typo, thanks.   

John


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## chandler Trev

I had built a mold and wondered this very topic.  How much oil to fill it.  I found you formula and walla, filled right to the top.  Thank  you


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## cwayneu

chandler Trev said:
			
		

> I had built a mold and wondered this very topic.  How much oil to fill it.  I found you formula and walla, *filled right to the top*.  Thank  you



That's great. Folks should keep in  mind that you don't always use the complete mold volume times .4 to figure your batch size.

This may be obvious, but for example we make all of our rectangular bars 3 1/2" by 2 1/2" by 1" thick. We have a log mold that is 3 1/2" wide by 30" long by 3" deep. We normally want the batter only 1" thick for face up bars so we can decorate. The bars come out side by side lying flat face up. That means we can make 12 bars (2 1/2" wide X 12 bars = the 30" length) by pouring the batter 1" thick. So we calculate 3.5 X 30 X *1* X .4 to get a batch size of 42 oz. However, we can also make 30 bars, on their side edge, from the same mold  by pouring batter 2 1/2" deep. This means our batch size would be 3.5 X 30 X *2.5* X .4  or 105 oz. Hope this makes sense.


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## cwayneu

*One final update for mold trays*

One other issue you may run it to is wanting to use a mold tray of some kind, like a silicone muffin pan, where it may tell you the total volume in ounces. We have a tray of hearts that says it holds 6.5 ounces. It won't be exact based on water weights, but 1 ounce of water converts to 1.8 cubic inches of water. So if the tray holds 6.5 ounces, that is 6.5 X 1.8 = 11.7 cubic inches.

Since that batch formula is always the mold volume in cubic inches times .4 to give you batch oil/fat ounces, then the tray batch size should be 11.7 X .4 = 4.68 (or about 4.7 oz. to put into soapcalc). This makes sense because you will be adding just under 2 oz. of lye water back into the oils/fats, which gets us back to about the 6.5 ounce tray size.

I found a free calculator some time ago that converts just about any units to about any units you want. In this case I used the volume tab to get the 1 oz. = 1.8 cubic inches. You can download it at

http://joshmadison.com/software/convert-for-windows/

Finally, if you don't know the volume or ounces of some weird shaped tray or mold, you can always put it on your scale, tare it out, and fill it with water. Then take those ounces times 1.8 times .4, like the above example. That's the number you put in soapcalc. 

Happy soaping...


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## Fuzled

cwayneu said:
			
		

> chandler Trev said:
> 
> 
> 
> 
> I had built a mold and wondered this very topic.  How much oil to fill it.  I found you formula and walla, *filled right to the top*.  Thank  you
> 
> 
> 
> 
> That's great. Folks should keep in  mind that you don't always use the complete mold volume times .4 to figure your batch size.
> 
> This may be obvious, but for example we make all of our rectangular bars 3 1/2" by 2 1/2" by 1" thick. We have a log mold that is 3 1/2" wide by 30" long by 3" deep. We normally want the batter only 1" thick for face up bars so we can decorate. The bars come out side by side lying flat face up. That means we can make 12 bars (2 1/2" wide X 12 bars = the 30" length) by pouring the batter 1" thick. So we calculate 3.5 X 30 X *1* X .4 to get a batch size of 42 oz. However, we can also make 30 bars, on their side edge, from the same mold  by pouring batter 2 1/2" deep. This means our batch size would be 3.5 X 30 X *2.5* X .4  or 105 oz. Hope this makes sense.
Click to expand...


So this means that I don't have to fill my mold to the very top? I've been reading this and using the mold size calc online, but have been wondering if it's ok NOT to fill my mold all the way up..


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## cwayneu

Fuzled said:
			
		

> *So this means that I don't have to fill my mold to the very top? *I've been reading this and using the mold size calc online, but have been wondering if it's ok NOT to fill my mold all the way up..



Exactly. You only make the soap as thick as you want, and the calculation has to be based on the thickness you want, not the absolute maximum limit of your mold.


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## Fuzled

What am I doing wrong to understand this? Every time I try to do my own calculations I end up with too much total liquid (I think) for the entire mold..no matter what mold size I try and run these with I end up with the problem listed below..

 Hoping some one can set me straight.. here's my math:

I have a 2lb (per the manufacture) mold that measures inside dimensions:
3.5in w x 9in l x 2.5 h= 78.75 cu in volume

78.75 x .4=31.5 oz of oils per the calculation, correct?

*Here's where I get confused*: 

2lbs mold =32oz 

When I run oil amt thru Soap Calc (ex. is 100% tallow) it says:

31.5 oz oils + 4.2oz lye +11.97 oz Water. This equals 47.67 oz of total liquid. 

This is way too much for my 32 oz mold, right? 

It seems everyone uses this formula, so I must be not understanding something.. Can anyone help me?

*EDIT:* I think I know where I'm screwing up. The 2.5in is the pour line, the 2lb listing is actually the amt of oils. So recalculating actual height of the mold is 3.5, giving 110.25 cu in which = 61 fl oz. This would account for the oil and lye water


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## cwayneu

Fuzled, not sure. The 2 lb label on your mold is confusing. Based on the conversion of 1 oz of water = 1.8 cubic inches, that says that 32 oz (2 lbs) times 1.8 = 57.6 cubic inches. Yet your 3.5 X 9 X 2.5 = 78.75 cubic inches. If we reverse that to find ounces we get 78.75 / 1.8 = 43.75 ounces, or 2.7 lbs. So I don't know what the 2 lb label refers to, since it is almost 3 pounds. 

I have checked the 1 ounce = 1.8 cubic inces with one of my molds and it holds pretty true. I have a 3.5" by 8" by 2.5" deep mold (= 70 cubic inces). It takes exactly 39 ounces of water (on my scale) to fill it to the top. And to check I took 39 ounces X 1.8 = 70.2 cubic inches (pretty darn close). So again, the 2 lb label on your mold seems to be bogus.

I do always keep a single bar plastic mold handy, in case I do have batter left over, so I can dump it in there.


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## Korgan

*My ol' spreadsheet*

Hey guys,

Few years ago, I wrote a very useful spreadsheet.  Now, I have no idea where you got the 0.4.  But I think some people were saying it worked for them so I won't criticise too quickly. 

What I do know is that this spreadsheet I made calculates the density of the soap of any recipe I give it.  So, I have my container, I fill it with water and then I weigh that water.  Then I enter that into the spreadsheet as well as the recipe.  The spreadsheet then calculates the density of that soap and scales the recipe automatically to fit into the given container.

Since the density of each oil is different, and most recipes have different oils, the density of each soap is always different.  So you can't give one number, like 0.4, and have it be correct all the time.  

Also, the spreadsheet automatically costs each ingredient in the recipe, gives me a total cost of the block of soap, and figures out a selling cost of the total block and each 100g bar.  Very handy!  :wink: 

Anyway, this is my first post in this forum and hope to have fun while I'm here.  

Also, what's with the near-impossible capcha codes on this forum?  Ridiculous.


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## IanT

That sounds so cool!!

As far as the codes...yeah they are a PAIN in the rear..but they only last for the first 10 or 15 posts to make sure youre not a troll or robot or something... I swear it took me like 2 weeks to finally get them to go away and I agree with you 100% they are a pain in the rear for sure!!!


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## cwayneu

You are totally correct in that every different recipe will have different densities, therefore different volume weights. It's a good idea, but the .4 is a rule of thumb published by several sources and seems close enough. I have my molds all labeled (like 42 oz. for example). I don't want to re-enter my recipe on every different batch just to be a perfect 1.00" thick. My bars may vary from 0.99" to 1.01", but no one can really tell the difference. If soapcalc did this for you, it would be cool. But like I said, re-entering the recipe into another tool just does not seem worth it. IMHO.


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## Korgan

I forgot to mention, my spreadsheet also calculates how much lye is required, so I don't need Soapcalc.   :wink: 

So as for having to type it into two programs, that's unnecessary.  I'm not a fan of any of the soap calculators online.


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## cwayneu

Korgan said:
			
		

> I forgot to mention, my spreadsheet also calculates how much lye is required, so I don't need Soapcalc.   :wink:
> 
> So as for having to type it into two programs, that's unnecessary.  I'm not a fan of any of the soap calculators online.



OK, now that's pretty cool.    So the next question is, how can we get our hands on your spreadsheet?


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## naturesphilosophy

*ok, just to be clear*

I wanted to do some sample batches or 1lb each and based on the calculations, it would take two of the cylindrical molds to hold one batch (I'm using plastic frozen juice containers to test the recipes).  My question, though is that this is just the oil measurement, correct?  So I would enter in the amount of oils into soapcalc and that would give me the total recipe (with water/lye) to make up the full batch?

So I enter, 1lb oil weight with the standard 38% water and use the end result.  Right?


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## cwayneu

Yes, you calculate the volume of your mold(s) times 0.4, and that is the total oil weight you enter into soapcalc. I am not certain, but believe it is the 0.4 times the volume that takes into account that you will be adding water and lye. By magic or whatever, it seems to work.


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## Best Natural Soap

*How much soap for a mold?*

Or... try this site:  
http://summerbeemeadow.com/content/sbm- ... pe-resizer
Their Recipe Resizer is great! Simply input your oils and percentages... it will give you a calculated recipe. Then, you can click "Recipe Resizer," input your mold's dimensions, and it will figure the weights of your oils/lye for you!


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## paillo

*Re: How much soap for a mold?*

That recipe resizer is fantastic, thanks so much for posting it!


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## SmellyKat

Soapmaker Man said:
			
		

> Hi everyone.I wanted to post this as a sticky so all could learn how much oils are needed for your mold.  Here is the way to figure it.
> 
> Lets use a log mold that is 12 inches long, 3-1/2 inches wide, and you want to pour to a depth of 2-1/2 inches.
> 
> You take length X width X height of pour, that number X .40.  So;
> 
> 12 X
> 3.5=
> 42
> 
> 42X
> 2.5=
> 105
> 
> 105X
> .40=
> *42 ounces of oils needed for this mold.*
> 
> Apply these same numbers for your mold size, weather a log, slab, or block. :wink:
> 
> Paul



Is that TOTAL oils??  Including the EO's if you use any??  So then you would have to divide those 42 oz in to the different oils.  Example: 20% coconut oil,, 10% Palm oil, 12 % Olive oil.
(Sorry I am new and trying to wrap my head around these calculations)


----------



## IanT

no worries!! that would be for total *base oils* in your recipe, additives are in addition to this number (so meaning any FOs or EOs are not included in that calculation and should be added extra in addition to it)



.... but yup, thats all youd have to do is divide the raw numbers into the total oils, converting them to percent and you can scale up or down your recipe to your specifications...

hope that helps!


----------



## CiCi

I used this calculation for my molds and it came up a tad bit short of what I needed to fill the mold. It worked better when I calculated x.42, instead of .40.


----------



## brianhood

*HOW TO FIGURE HOW MUCH OIL FOR A MOULD*

i found details on this site very useful
www.soap-making-essentials.com

hope it helps


----------



## savondebilal

*Oils in mold (dimensions) - Bilal Hito*

fill it up with water for an easy, approximate measure of how much oil youd need

- bilal hito bilalhito BILAL


----------



## judymoody

I finally figured out a formula that works for me that is stone simple.  I use grams instead of ounces when soaping so I can be more precise with measurements.  100 grams of oil = 1 inch of loaf mold length with a bar size of 2.5 x 3.5.  So 12 inch mold = 1200 grams of oils.  My lye to water ratio is generally 1:2.  My bars weigh about 140 grams (5 oz) when freshly cut, give or take a little depending on whether or not I use any additives: milk, vegetable purees, honey, oats, clay, etc.  Hope this helps somebody.


----------



## Guest

*An easier mold size calculator*

I found this works well, without having to calculate anything yourself:


[Edited by SMF Modmin Team to remove non-functioning link]


----------



## drdave46

*Thank you... Thank you*

From a newbie who has been struggling with this - THANK YOU!!!

I havent made my first batch yet because I couldn't figure out how much to use, now I can get started..... wish me luck.


----------



## jadiebugs1

*Re: An easier mold size calculator*



			
				AngelMae said:
			
		

> I found this works well, without having to calculate anything yourself:


 
what IS this link??

[Edited by SMF Modmin Team to remove non-functioning link]


----------



## ctay122

*How to determin how much oil to use per mold*

Summer Bee Meadow also has a calculator that will do this for you. It works very well, especially if you are using an odd shaped mold or a cardboard box. It will take the recipe you type in for the lye calculator and resize the oils for you.


----------



## delicious

I am completely ignorant when it comes to ounces and inches, so I did the math to figure out what it would be in cm and grams.

Take the volume in cubic cm (Length x Width x Height).
Divide that by 2,54^3 (which is 2,54 x 2,54 x 2,54) = 16,39 (to get the cubic cm into cubic inches).
And multiply by 28,35 to convert that into ounces.
Then multiply by the 0,4.

So it's:
(L x W x H) / 16,39 x 28,35 x 0,4

Which is the same as :
(L x W x H) x 0,692

That's for the metric users.


Please note: I have not tested this formula so use at your own risk! Althouth the link given by TopCat  gives 0,657 for metric users... I don't know where it comes from but it is very close to what I found.


[Edited by SMF Modmin Team to remove non-functioning link]


----------



## booboosoaps

This formula is great.  It has worked for all my odd molds.


----------



## Ifiyenia

Somehow, it doesn't work for me... I guess I'm the only one


----------



## cwayneu

Ifiyenia said:
			
		

> Somehow, it doesn't work for me... I guess I'm the only one



Not sure how this works either. The rule of thumb I have always seen is L X W X D (or the volume) in inches multiplied by .4. 

So I get the divide by 16.39 to convert cubic centimeters to cubic inches, but don't understand the convert to ounces at all. A one cubic inch volume of water converts to about 1/2 of one ounce (or .554 ounces more exactly) so I don't where the 28.35 comes from. One UK ounce converts to 28.41 cubic centimeters, but that's still not 28.35.


----------



## SudsyKat

Just tried this calculation over the weekend - I had a new large mold and wasn't sure how much soap to make. Anyhow, it was kind of close, but did not make enough soap to fill my log mold to the desired height. I even added 4 oz of oils just for good measure (it's a 22 inch log mold). I think the difference is in the amount of water (or lye concentration) you use. I was using a fairly low water amount (33% lye concentration). I know people frequently use more water than that, so I'll have to take that into account next time. Is 38% pretty much the standard (I saw someone else on this post mention it)? I've used all different amounts, depending on the recipe.  To the original poster - thanks for posting this. It was helpful to get a general idea of the amount.


----------



## BBrandDesign

Wooden soap molds are no longer the only option out there to use for soap making. In all honesty, you can pretty much use not anything as long as it does leak, and does not react with the soap and you can get the soap out of it later.


----------



## tlm884

I recently found out why you multiply the volume of the mold by .4. The .4 is actually the percent of Water as a % of oil. It looks like the formula here uses 40% instead of the standard 38%. 

So, if you are using 38% you would multiply the volume of the mold (width X height X length) in cubic inches by .38. This will give you the amount of oil the mold will hold when 38% water is used. 

So, if you are using a different amount of water, the mold will hold a different amount of oils. However, the mold will always same the same volume of soap.


----------



## chibilightangel

The best mold size calculation come from TheDish soap forum. It's a metric calculation but so far has proven as most accurate for me as I can change my water and know by how much I should adjust the recipe.

Metric calculator found here: http://www.thedishforum.com/forum/index.php?showtopic=149087&st=0&p=2629990&#entry2629990

conversion factors: 28.35g per oz (weight)
                             2.54 cm per inch

Works for any size mold provided you can calculate the volume.


----------



## Iris Reola

I'm going to attempt this in reverse to find the final dimension for a mold needed to fit 35 ounces of oil so that my father can build me a mold to suit my needs. I'll let you guys know how that works out and whether or not I completely suck at algebra. 8D


----------



## Robbiegirl

Where does the .40 come from ? That might be a percentage of volume. So in a typical recipe of soap is 40 percent of the volume from oils?


----------



## majstor

I made a spreadsheet for calculating volume of mold and components (lye, water and oils)

https://docs.google.com/spreadsheet/ccc ... DBWMDZWWWc

Its work in progress, in green fields you are putting numbers for your case.


----------



## soxysarah

dose this work with cupcake moulds ?


----------



## danahuff

Well, I know this is an older thread now, and maybe no one cares, but l*w*h is the formula for the volume of a rectangular prism. A soap recipe is comprised of more than just the oils, hence multiplying it by 0.4. I imagine that at some point, someone calculated that unsaponified oils totaled about 40% or 0.4 of the total volume of the batch when it's at trace. However, that person is way smarter than me. I kept making too much soap for my mold until I happened on this formula somewhere else. I was trying to total the volume of liquids—oils + lye—and it wasn't returning the right results.


----------



## shafaq007

When we multiply the LxWxH are we measuring in inches or centimeters. I have seen a similar formula except it says to multiple the result by .38.


----------



## Relle

Example

Lets use a log mold that is 12 inches long, 3-1/2 inches wide, and you want to pour to a depth of 2-1/2 inches.
You take length X width X height of pour, that number X .40. So; 
12 X 
3.5= 
42 

42X 
2.5= 
105 

105X 
.40= 
42 ounces of oils needed for this mold.  Apply these same numbers for your mold size, weather a log, slab, or block.

Work it out in inches and then convert the volume if you want metric. 42 ounces is 1190.7 grms.


----------



## mzz

For metric I use:
Volume (cm3) x 0.7 = ? g oils


----------



## jkoehn

Thank you sooo much!


----------



## soapbuddy

I go by length X height X width, then multiply all by 0.37 That seems to give me the most accurate measure.


----------



## Cherry Bomb

*Math Enthusiast*

SoapMaker Man, thank you so much for posting this formula! I love chemistry and I love math! Working your EO quantities needed out on paper will help me feel like I have accomplished something magical! Lol I had planned on using the following link to figure out my EO quantities but your way seems like more fun! Just call me insane in the membrane! 

http://www.brambleberry.com/Pages/Fragrance-Calculator.aspx

This link is also a good way to figure out your lye %. Once you calculate your lye % this link will also give you your total weight and you can use that to plug into the fragrance calculator or use your method! 

http://www.brambleberry.com/Pages/Lye-Calculator.aspx

Anyways, I am new to this and from a newbie....this was great information! Thanks again and have a "Soap"tacular day!!!!


----------



## souljasam

so i was trying to do this to figure out how much i needed for my 13" x 3.5" x 2.5" mold in order to make a 4 pounds of soap like the mold should hold. 

2.5
3.5=
8.75

8.75
13=
113.75

113.75
.40=
45.5oz of oil

now when i put that into the lye calculator on soapcalc.net it says i need 17.29 oz water and 5.856oz lye. now

45.5+17.29+5.856=68.646 about 4.5 oz more than 2lbs(64oz)

what am i doing wrong? ive even tried it with .38 to get 43.335oz of oil to get an end total of 65.214oz. closer but still over an oz off.


----------



## Nevada

The cured Soap will lose around 4.5 oz of water due to evaporation. 
You'll be fine


----------



## souljasam

ahhh, ok. i figured some evaporation would occur but wasn't sure how much. thanks a lot.


----------



## becca757

*how much oil to use....*

Soapmaker....does your method include the water and the lye?  I'm fairly new to making cp soaps and I'm having trouble with calculating the volume of my mold.
I have a wood mold that is 7 in long,  3.5 in wide and 2.75 in high.  Now from my research I was told to multiply the length x width x height which I have and got 67.3.  Then was told to multiply that by 0.554 to get 37.2 and then multiply that by 0.9 for a total of 33.5 ounces.  I've done that and for some reason when I go to fill my mold I end up filling my mold to the top and still have more soap left over.  Would you mind terribly giving me some advice on how to correct that?  Thank you so much in advance!!


----------



## Bann51

No. It doesn't include the lye.  It tells you the oils. Because I'm new to cp. I started with small wooden boxes I got from the craft store.  I did the measurement and came up with my oils.  After doing the calculations for them, they called for a 24 oz recipe.  I use that for my soap recipe and it fit perfectly into my boxes. So if you do your calculation of 7 x 3.5 x 2.75 you get 67.375 then multiply that by .40, you get 26.95 So your soap recipe should be 27 ounces in oils. Of couse once you run it through a lye calculator, you'll get the water and lye.  This is the way I've seen it done on several websites.


----------



## Armydeuno

Im new to all this, so excuse my ignorance.

I know this is subjective, but how much fragrance/essential oil can be added per pound of CP soap?

Thanks!


----------



## Bann51

Um. I would do a search and get as much information as possible. Your soap making books will be offering suggestions. Not all essential oils and fragrance oils work the same.  Most of the time it's suggested that you use less essentials than you would fragrance oil in a batch. Also, some companies that you purchase from may have suggestions for their particular fragrance oil. Some tell you specifically how to use a particular oil for a particular strength. I am also a new cp soaper, though I have made M&P for over 10 years. Reading and doing research, I find, is the best teacher. If you can't afford to buy books there is great information out there on the internet. Good luck.


----------



## pahbi

*How was the .4 calculated?*

I apologize in advance for my poor search abilities.

Background:

For several months, I have used the basic formula (H * W * L) * .4 to convert the volume of my mold into the amount of oil to put into a lye calculator.

This method has worked just fine for me.

However, it bothers me that I can't figure out how the .4 was calculated.

I read the stickied thread about calculating oil using the .4 rule of thumb, and it was suggested that the .4 was related to the amount of water that is being mixed with the lye.  That sounds reasonable, but to date, I just can't seem to recreate that math.

I have been able to accurately calculate the weight of a oil in grams that will fill a particular mold using the density of the oil to convert from volume to fluid ounces, and then to ounces, and then to grams.

But reverse engineering the .4 is just baffling me.

Does anyone have a link or explanation or just the full formula for how the .4 was derived?

Thanks in advance,
- Paul


----------



## Nevada

I suspect it is anecdotal, someone took notes and "Reversed Engineered" the calculation :idea:
Just my 12 cents (inflation adjusted) ;-)


----------



## sososo

I will try to explain (sorry for my english).
I wil use grams and cubic centimeters, than I will convert in ounce and cubic inch.

First, 3 facts:
1. The density of oils is 0.900 - 0.920 grams / cubic centimeter - for example, the density of OO is 0.918 - see here: [Link no longer functional. Removed by SMF Modmin Team]
2. The density of lye is 2.13 g/cm3. See here:
http://en.wikipedia.org/wiki/Sodium_hydroxide
3. The density of water is 1 gram/cm3 (no link, belive me!)

Let's say that we want to make a 100% olive oil soap using 1000 grams of oil, 0%SF, 33% lye concentration. SoapCalc gives us:

Water - 275.05 g
Lye - 135.472 g

So we have this volumes (I divided the quantities by densities):
Oil - 1000/0.918 = 1089.325
Water - 275.05/1 = 275.05
Lye - 135.472/2.13 = 63.60
--------------
Total volume - 1428 cm3

1000 g (oil) means* 35.274 ounces* and 1428 cm3 (total volume) means* 87.14 cubic inches*
Now, the final calculation:
35.274/87.14 = 0.404797 = (aprox) *0.4*

Quod erat demonstrandum.


----------



## pahbi

Sososo,

Thank you for taking the time to explain, that does indeed explain the origin of .4

I'm now faced with a new problem.  I would like to put this information into a spreadsheet.

Your math skills seem stronger than mine, so let me pose this question:

Based on the information in your example, how would you compute the amount of OO to use, using only the following information:

ps.  Please leave all of the calculations in metric.

1)  Height, length and width of the soap mold.
2)  Density of Olive oil, water and lye.
3)  33% lye concentration.
4)  SAP value of Olive Oil.

Thanks,
- Paul


----------



## sososo

pahbi said:


> Sososo,
> 
> Based on the information in your example, how would you compute the amount of OO to use, using only the following information:
> 
> ps.  Please leave all of the calculations in metric.
> 
> 1)  Height, length and width of the soap mold.
> 2)  Density of Olive oil, water and lye.
> 3)  33% lye concentration.
> 4)  SAP value of Olive Oil.
> 
> Thanks,
> - Paul


First, some notations:
height=H
length=L
width=W
oil density=OD
water density=WD
lye density=LD
oil weight=OW
water weight=WW
lye weight=LW
oil volume=OV
water volume=WV
lye volume=LV
SAP=SAP (!)

We calculate total volume (TV) in two ways:
First:

TV=H*L*W

Second, more complicated but not very complicated.

LW=OW*SAP
WW=LW*(100-33)/33=LW*67/33=(aprox) LW*2=OW*SAP*2
OV=OW/OD
LV=LW/LD=OW*SAP/LD
WV=WW/WD=OW*SAP*2/WD
So, 
TV=OV+LV+WV=OW/OD+OW*SAP/LD+OW*SAP*2/WD=OW*(1/OD+SAP/LD+SAP*2/WD)

Now we have this equality:
H*L*W=OW*(1/OD+SAP/LD+SAP*2/WD)

And finaly:
*OW=(H*L*W)/(1/OD+SAP/LD+SAP*2/WD)*

This formula is ok not only for grams and cubic centimeters but also for ounces and cubic inch.


----------



## DeeAnna

Here's an Excel spreadsheet version. I made it more generic, so it can be used with any soap recipe.

The first image is what it looks like when you use the spreadsheet normally. The second image shows the formulas within the spreadsheet cells that do the calculations. The formulas are the parts that start with equals (=) signs. 

I did not use saponification values or lye concentration in this spreadsheet. I assumed the user would start with an existing recipe, so all of the oil, lye, and water weights are already known. It could be used with units of ounces (wt) and inches as well -- I'd just change the units in the table headings and convert the default density from 0.91 g/cm3 to 0.53 oz/in3.

I can't upload a spreadsheet to the forum. If anyone wants a copy, I will be happy to provide it. I can't send spreadsheet files through SMF, so please send me a PM with your _direct email address_ and let me know what units you want to use -- _ounces or grams_.

Or if you have suggestions for improvement, let me know that too. This is just a quick 'n dirty first try.


----------



## pahbi

Sososo,

Thank you for working on the math for this, I really enjoy seeing how things are calculated.

When I saw your post on my cell phone I was very excited, so I rushed to the computer when I got home from work and tried out the formula.

But I must be doing something wrong, and I'm hoping you can spot my error.

I'm using your final derived formula of:

OW=(H*L*W)/(1/OD+SAP/LD+SAP*2/WD)

The values I'm plugging into the formula are:

L = 55 cm
H = 6 cm
w = 10 cm
OD = .91
SAP = 190
LD = 2.13
WD = 1

The formula gives me 7.016 grams, but I should be getting over 2000 grams.  I must be putting a wrong value into the formula somewhere.  Could you look over my math and see if you can spot where I goofed?

Thanks,
- Paul

I changed my sap value from 190 to .190 and I am getting an answer that seems more in line with the expected result.  Was that my error?

- Paul


----------



## bodhi

DeeAnna, what is the third value for dimensions that self calculates, and why .91 for a default density?


----------



## sososo

pahbi said:


> I changed my sap value from 190 to .190 and I am getting an answer that seems more in line with the expected result.  Was that my error?
> 
> - Paul


Yes, this was the error. 0.190 is the correct value to use.
SAP=190 means that you need to use 190 miligrams of lye at each 1 gram of oil. But, because we have to use the same measure unit, the correct value is 0.190 - so, we ned 0.190 grams of lye to saponify 1 gram of oil.


----------



## DeeAnna

"...why .91 for a default density..."

According to Sososo's Post #3, the density of oils ranges from 0.900 to 0.920 g/cm3. I took this info at face value. The average between 0.9 and 0.92 is 0.91 g/cm3. If you have a suggestion for a more accurate default density for typical soaping oils, I'm all ears. 

I reverse engineered the "0.4 formula" awhile back, and I'm reasonably certain it assumes a default oil density somewhere around 0.9, give or take a bit. It also assumes the soap recipe is made with "full water" which over estimates the soap volume if a soaper uses a more concentrated lye solution.

"...what is the third value for dimensions that self calculates..."

A rectangular mold has length, height, and width. If you know the volume of the soap recipe and you know any two of the linear dimensions of the mold, you can calculate the third linear dimension. Many people have a mold and want to know how deep a batch of soap will be in the mold. Or they have a specific bar size in mind and want to know how long of a loaf mold to buy. This calculation helps answer those questions. 

A similar calculation could be done for round molds too. Given the volume of soap and the diameter of a Pringles can or PVC pipe, how tall does the mold have to be?


----------



## sososo

DeeAnna, if you put on a column in your spreadsheet the SAP values of the oils, you can calculate the lye amount and then, using a certain concentration value (say 33%) you can calculate the water amount. Now these two (lye and water) are manualy entered in your spredsheet.


----------



## sososo

DeeAnna said:


> A similar calculation could be done for round molds too. Given the volume of soap and the diameter of a Pringles can or PVC pipe, how tall does the mold have to be?


Pringles can you say? Good idea!!! Thank you!


----------



## bodhi

Aah, i skimmed the posts until i got to the calculations so i missed that.  Nope, no suggestions but ill poke around and if i see anything interesting ill let you know.  I did find this which you may find useful in your recent experiments.  Stearic has a density of .8387 at 180'f.  What temps are you norm-ing to on your sheet?

'Many people have a mold and want to know how deep a batch of soap will be...' No kidding!  Now that you say it, that is so obvious i should be embarrassed, LOL.  It completely baffled me because i couldnt figure out how in the world this would allow me calculate for the depth i wanted-which is how i calculate for volumes-and that's why, its a predetermined recipe, duh, lol.  Thank you DeeAnna


----------



## pahbi

Sososo,

I worked the formula into a spreadsheet, and then compared my results to soapcalc, and my values came out close, but the values are far enough off to cause concern.

You've been awesome, and I feel guilty to ask this, but would you be willing to work the math for a soap recipe so I can check myself and make sure I'm doing the formula right.

My soap recipe is:

60% olive oil
30% coconut oil
10% sunflower oil
33% lye solution

My mold is 22"L x 3.875W x 2.5"H

Thanks,
- Paul


----------



## DeeAnna

Sososo:

"...if you put on a column in your spreadsheet the SAP values of the oils, you can calculate the lye amount and then, using a certain concentration value (say 33%) you can calculate the water amount..."

Yes, I completely agree that could be done on the spreadsheet. By calculating the lye and water from the saponification values and lye concentration, you're basically making a very basic soap recipe calculator. That would be easy to include in the spreadsheet. But...

I was trying to think how most people would use this type of thing, based on what I have read here on SMF. The appeal of the "0.40 rule" is that it distills the calculations into to a single, simple algebra problem. You and I might prefer to do the calculations and make our own assumptions, but many people don't want to do that. I've seen soapers who are having trouble using the 0.40 rule correctly, simple as it is. 

I decided the sap values would probably make it harder for an everyday person to use the spreadsheet, since most people would not have the sap values unless they look them up in a soap recipe calculator like SoapCalc. A "real" recipe calculator like SoapCalc is the better place to do the recipe design. Then bring the basic data back to the mold volume calculator and go from there.

I don't use SoapCalc much, because I designed a soap recipe calculator on a spreadsheet that tries to account for all the fine details that you and I like to know. Among other things, the spreadsheet calculates the total batter volume, the number of bars the recipe will make based on the bar weight, the approximate cost per bar, and even the size of the soap pot I need to use. My calculator spreadsheet also includes a database of the properties of fats, including NaOH and KOH sap values, so I don't have to look that information up. It would be easy to add a section to calculate mold volume. 

Bodhi: "... Stearic has a density of .8387 at 180'f. What temps are you norm-ing to on your sheet?..."

This thread is about reverse engineering the "0.40 rule" to get a better understanding of the thinking that went into creating the 0.4 rule and to make it more accurate, but I didn't think the goal is to be laboratory precise. Not many people, IMO, add more than a few percent of stearic fatty acid to a typical recipe, if they add any at all, unless they are making shaving soap. I'd say a density estimate of 0.91 or thereabouts is close enough, even for stearic acid, to estimate the volume for most soap recipes most of the time. 

But if a mold volume calculator were to include a database of sap values, why not include density values too, hey? It's certainly do-able, but I wonder if the increased accuracy is worth the extra complexity.

And on that note -- if someone is making a soap with a lot of filler material -- say a salt bar with 80% salt, or a whipped soap, or a soap with pureed botanical ingredients like pureed papaya -- then the mold volume calculations in this thread will not be accurate. I suppose the calculator could allow the user to include this information too.

And this is rapidly getting rather complicated, even for me! I feel like a kitten tangled in a large ball of yarn.


----------



## bodhi

DeeAnna said:


> I don't use SoapCalc much, because I designed a soap recipe calculator on a spreadsheet that tries to account for all the fine details that you and I like to know. Among other things, the spreadsheet calculates the total batter volume, the number of bars the recipe will make based on the bar weight, the approximate cost per bar, and even the size of the soap pot I need to use. My calculator spreadsheet also includes a database of the properties of fats, including NaOH and KOH sap values, so I don't have to look that information up. It would be easy to add a section to calculate mold volume.
> 
> Bodhi: "... Stearic has a density of .8387 at 180'f. What temps are you norm-ing to on your sheet?..."
> 
> This thread is about reverse engineering the "0.40 rule" to get a better understanding of the thinking that went into creating the 0.4 rule and to make it more accurate, but I didn't think the goal is to be laboratory precise. Not many people, IMO, add more than a few percent of stearic fatty acid to a typical recipe, if they add any at all, unless they are making shaving soap. I'd say a density estimate of 0.91 or thereabouts is close enough, even for stearic acid, to estimate the volume for most soap recipes most of the time. But if a mold volume calculator were to include a database of sap values, why not include density values too, hey? It's certainly do-able.



Yes, i did digress and that is indeed a topic for another thread.  I was just thinking ahead to my calculator-which is similar to yours minus the quick and dirty soap calc for now.  (Nice idea including the pot sizes!) And hey why not calculate everything on the same sheet.  :crazy:  This thread just had me thinking about the totality of it again and if im incorporating concentrations, then why not densities and at the same temps too.  I agree .91 is a good enough for the great majority of uses though.  I just thought you might like the stearic bit but on second thought you probably already had that. 



DeeAnna said:


> And this is rapidly getting rather complicated, even for me! I feel like a kitten tangled in a large ball of yarn.   :razz:


  You can say that again!

So back to the .4, I hadn't incorporated the volumes into my spreadsheet yet because the .4  was hit or miss -i rarely use full water.  These posts are sorting out the math which i find boggling so I may now be able to account for the various concentrations.  Im very grateful this was brought up again and for the fabulous breakdowns in calculations.


----------



## pahbi

For me, this thread has been extremely helpful, and I'm thankful for everyone, who has taken the time to participate.

This thread is a good canidate for stickying imo.

- Paul


----------



## DeeAnna

"...the .4 was hit or miss -i rarely use full water..."

Yep, same here. I am wary of swallowing "common wisdom" without first chewing it well. When I read about the 0.4 rule, I took the time to figure it out for myself. I realized it would overestimate the size of my molds, so I just did the math from scratch to figure the mold sizes I wanted. 

On a slab mold, oversizing the depth of the mold is not a big deal. But for a loaf mold, the bar size and shape can get really messed up if the volume calculation is not reasonably accurate.


----------



## sososo

pahbi said:


> Sososo,
> 
> I worked the formula into a spreadsheet, and then compared my results to soapcalc, and my values came out close, but the values are far enough off to cause concern.


Don't foget to put in soapcalc: 0%SF and "Lye concentration"=33% - because these are the values I used in my formula. And pay atention to SAP value to be the same as in soapcalc.





pahbi said:


> You've been awesome, and I feel guilty to ask this, but would you be  willing to work the math for a soap recipe so I can check myself and  make sure I'm doing the formula right.
> 
> My soap recipe is:
> 
> 60% olive oil
> 30% coconut oil
> 10% sunflower oil
> 33% lye solution
> 
> My mold is 22"L x 3.875W x 2.5"H
> 
> Thanks,
> - Paul


Ok, let's see. So now you have 3 oils, not just one. In general, I will use the same demonstration I used for one oil but now we have three oil density - OD1, OD2, OD3, three SAP values - SAP1, SAP2, SAP3, three oil weights - OW1, OW2, OW3, three oil volumes - OV1, OV2, OV3 and thre oil percentages - P1, P2, P3.

LW=OW1*SAP1+OW2*SAP2+OW3*SAP3
WW=LW*(100-33)/33=LW*67/33=(aprox) LW*2=(OW1*SAP1+OW2*SAP2+OW3*SAP3)*2
OV=OW1/OD1+OW2/OD2+OW3/OD3
LV=LW/LD=(OW1*SAP1+OW2*SAP2+OW3*SAP3)/LD
WV=WW/WD=(OW1*SAP1+OW2*SAP2+OW3*SAP3)*2/WD
So, 
TV=OV+LV+WV=OW1/OD1+OW2/OD2+OW3/OD3+(OW1*SAP1+OW2*SAP2+OW3*SAP3)/LD+(OW1*SAP1+OW2*SAP2+OW3*SAP3)*2/WD

Now we will write OW2 and OW3 using OW1:
OW2=(OW1*P2)/P1
OW3=(OW1*P3)/P1

So, TV using only OW1 is:
TV=OW1/OD1+(OW1*P2)/P1/OD2+(OW1*P3)/P1/OD3+(OW1*SAP1+(OW1*P2)/P1*SAP2+(OW1*P3)/P1*SAP3)/LD+(OW1*SAP1+(OW1*P2)/P1*SAP2+(OW1*P3)/P1*SAP3)*2/WD

or:
TV=OW1*(1/OD1+P2/P1/OD2+P3/P1/OD3+(SAP1+P2/P1*SAP2+P3/P1*SAP3)/LD+(SAP1+P2/P1*SAP2+P3/P1*SAP3)*2/WD)


so:
*OW1=TV/(1/OD1+P2/P1/OD2+P3/P1/OD3+(SAP1+P2/P1*SAP2+P3/P1*SAP3)/LD+(SAP1+P2/P1*SAP2+P3/P1*SAP3)*2/WD)
*
...and now, that you know OW1, for calculate OW2 and OW3 you have these two:
*OW2=(OW1*P2)/P1
OW3=(OW1*P3)/P1*


----------



## pahbi

Thank you Sososo, I achieved success with my spreadsheet.

I created a mold with small blocks that can be adjusted based on the size of the soap loaf to create.

I can now input the measurements of the mold into my spread sheet, and be confident I have accurate calculations.  My values compare almost exactly with Soapcalc, with the only differences due to me rounding to the nearest gram.

The next step will be to upload the spread sheet to Google Docs, so that I can access the spreadsheet on my android tablet.

I will need some time to really digest and understand all of the calculations.

Thanks again,
- Paul


----------



## bodhi

DeeAnna said:


> "...the .4 was hit or miss -i rarely use full water..."
> 
> Yep, same here. I am wary of swallowing "common wisdom" without first  chewing it well. When I read about the 0.4 rule, I took the time to  figure it out for myself. I realized it would overestimate the size of  my molds, so I just did the math from scratch to figure the mold sizes I  wanted.
> 
> On a slab mold, oversizing the depth of the mold is not a big deal. But  for a loaf mold, the bar size and shape can get really messed up if the  volume calculation is not reasonably accurate.



Exactly!   Except math isnt my strong suit so i figured, 'hey cant hurt to try it  anyway'.  Yeah.  I was scurrying for molds mid pour.   When i actually  sat down to figure it out i got as far as the water concentrations and  stopped because i couldnt deal with trying to figure the calculations.   Now I see why, lol.  

And bravo Sososo!  Kowtow, kowtow.


----------



## sososo

Not very complicated. I'm happy that this calculations will help somebody.


----------



## Hazel

Thanks everyone! I've merged this topic with the sticky "How to figure how much oil for mold" since it is related to the thread and made a permanent redirect to it.


----------



## BrambleNBumble

Newbie here and I'm still confused on how to figure out how much oil to use for a mold.  I bought a three pound mold but all the recipes I'm finding are for five pounds or higher.  Is there an easy way to figure this out or is it more trial and error?


----------



## alaskazimm

Easiest way I've found is to use the formula in the first post to find the weight of oils for your mold. Then convert the weights of the oils to % of recipe and run that through a lye calculator of choice. Example: For a 3 oil basic bar the posted recipe

Coconut Oil  270 gr
Olive Oil      360 gr
Palm Oil       270 gr

Convert that to % of recipe and you get

Coconut 30%
Olive   40%
Palm 30%

My small mold takes 695 gr of oil so plugging all that into my lye calculator comes out with

Coconut 209 gr
Olive   278 gr
Palm   209 gr

hope that helps.


----------



## gruntedsoaps

bodhi said:


> Exactly! Except math isnt my strong suit so i figured, 'hey cant hurt to try it anyway'. Yeah. I was scurrying for molds mid pour. When i actually sat down to figure it out i got as far as the water concentrations and stopped because i couldnt deal with trying to figure the calculations. Now I see why, lol.
> 
> And bravo Sososo! Kowtow, kowtow.


 

I have never moved so fast for a muffin pan ever in my life. lol.  Im new so I tried it blindly.  I WAS WAY OFF. were talking it filled my loaf pan and a muffin pan.  and they were all filled to the top, the loaf pan actually has a mountain on it. lol.  whatever it worked and I got all the soap I could.


----------



## A1will

Post for future. Reference


----------



## G Str

I'm not sure if this has been pointed out so far, but the 0.40 thing works only for imperial; inches and ounces.
If you use metric, grams and centimeters you must use about 0.70.

Proof:
say you want to fill a mold with dimensions of 2x3x4 (in inches). The volume is 24 cubic inches. You do the 0.4 thing and get 9.6 oz of oils.
now try that in cm. 1 in = 2.54 cm, so the dimensions of mold will be 5.08x7.62x10.16 in cm. That's a volume of 393.29 cubic centimeters. Do the 0.4 thing and you get a number of 157.32. What's that? Grams? Let's check. 1 oz. = 28.35 grams. 157.32/28.35 = 5.55 oz. You're 4.05 oz. short. Now try it with 0.7. 393.29x0.7 = 275.3, convert to oz. and you get 9.7 oz of oils. Now that's more spot on.
Where I'd get 0.7? From sososo's calculations, the same way he proved the 0.4 thing.

So long story short, it's 0.4 for ounces and inches, 0.7 for grams and centimeters.


----------



## The Efficacious Gentleman

Not sure if it's already been covered, but for those that struggle with maths, you can use the formula for calculating how big the mold needs to be depending on the size of your batch - 

Let's say I have a 7x5x2 inch mold - that's 7x5x2x0.4 to work out the oz of oils = 28 oz.

But I'm making a new mold (will swap to metric as that is what I'll be working in)  and I want to make a 550gm batch 8cm wide, 5cm deep.  To work out how long my mold would be is 550/0.7 (for metric!) /5/8 = 19.64cm long.  Oils/0.7/height/width.

Now 19.64 is a pain to get and wouldn't give me regular sized soaps, so I can work out the depth I'd get if I made it 20cm long - Oils/0.7/width/length = depth.  550/0.7/8/20 = 4.9cm deep.


----------



## MoonBath

:Kitten Love: I'm not a math person at all. So, this is probably a stunningly stupid question, but how does this solve for the space the water takes up?


----------



## tryanything

It's magic!  Seriously, just go with it.  It works.  I'm no math person either but I've successfully used this formula for many different mold shapes.  Maybe someone else will chime in with a more technical answer.


----------



## brigettevelasquez

Hi soap makers! Im a new soap maker and new in SMF as well. I have this homemade wood loaf mold and i was able to figure out how much oil to use by weighing the mold and then i press tare on my weighing scale and pour in rice grains inside.


----------



## new12soap

MoonBath said:


> :Kitten Love: I'm not a math person at all. So, this is probably a stunningly stupid question, but how does this solve for the space the water takes up?


 
It doesn't exactly solve for it, but it does take it into account. The _volume_ of water in 1 cubic inch is 0.55 ounces. The same _volume_ of oil will _weigh_ less than that because oil is less dense than water (that's why when you mix oil and water, say in your salad dressing, the oil will float on top). Using 0.4 ounces of oil (by _weight_ which is how we measure when making soap) per cubic inch of mold space, that allows for the addition of water and lye.

Remember, we are converting volume measurements to weight. This is a very simple formula that allows for using FULL water, and then the user can adjust for water discounts or additives.

It does work!


----------



## The Efficacious Gentleman

brigettevelasquez said:


> Hi soap makers! Im a new soap maker and new in SMF as well. I have this homemade wood loaf mold and i was able to figure out how much oil to use by weighing the mold and then i press tare on my weighing scale and pour in rice grains inside.View attachment 5727


 
Have you done the calculation too, to see if they marry up?


----------



## brigettevelasquez

Yes i computed using soapcalc. So if my total oil weight is 500g + 35% of water the soap mixture will fit my mold


----------



## The Efficacious Gentleman

How does that compare with the w x h x l x 0.7 calculation on the mold space?


----------



## brigettevelasquez

Rice grain weight = 700g

So if your water percentage is 35%

700g * 0.35 = 245g (water weight)

700g - 245g = 455g (oil weight)

 haven't tried the formula WxLxH x 0.7 but will try it soon


----------



## The Efficacious Gentleman

brigettevelasquez said:


> Rice grain weight = 700g
> 
> So if your water percentage is 35%
> 
> 700g * 0.35 = 245g (water weight)
> 
> 700g - 245g = 455g (oil weight)
> 
> haven't tried the formula WxLxH x 0.7 but will try it soon


 
Please do!  I'm interested to find out more about your measurements................... :grin:


----------



## brigettevelasquez

I use this same method in making silicon mold so i can figure out how much silicon rubber to use for my mold. And i tried it on my first batch of soap and it worked!


----------



## Saponista

Wxlxh x0.7 worked like a dream for me


----------



## Dennis

I would pull my hair out (what's left of it) if I tried to be as accurate as so many of you.  :crazy:  As a notorious rule of thumber, I use the L x W x D x 0.4 for capacity of oil and then weigh everything in grams that is so thoughtfully presented along with ounces by SoapCalc even if I've requested only ounces.  My penchant for the rule of thumb observance makes grams much closer than ounces.  When over by a gram or two I'll subtract a gram or two with the next ingredient - maybe.  After all, what's a silly little gram?  Now, if I tried that with ounces I would probably be in trouble.    It has always turned out ok but it is *Reason #42* that I make soap for fun and don't sell it.


----------



## jude20

This forum is really helping me. Thank you guys for sharing some knowledge...


----------



## scottief

*how much oils*

I understand how to get the amount of oils to use.  How do I determine how much of each oil to use once I know the loaf oil size?  Or can I just add a certain amount of each oil until I hit the loaf amour size. thanks for any help


----------



## Saponista

Just make up the total oils you have to the volume you have calculated for your mold. You can add whatever ratio of oils your recipe states. I would run it through soap calc to double check you still have the right amount of lye etc. if you are upscaling your recipe.


----------



## Dennis

scottief said:


> I understand how to get the amount of oils to use.  How do I determine how much of each oil to use once I know the loaf oil size?  Or can I just add a certain amount of each oil until I hit the loaf amour size. thanks for any help



I use soapcalc and play with different percentages of oils to balance out the characteristics I'm looking for.  Play around with it for a while and it will become a buddy.  If you've not looked at it yet, go to http://soapcalc.net/, click on soapcalc lye calculator, look around and start having fun.
There are others, but I'm comfy with soapcalc.


----------



## Sprag

Thanks !


----------



## Bubli

Do a google search for"How do I Calculate How Much Soap to Make to Fit My New Mold?"A really good article tutorial by David Fisher on About.com comes up.He shows you how to do ALL these calculations then how to determine the amount of each individual oil in your recipe to fit any mold.Its waaaay easier than it seems.Trust me,I'm no genius and I GOT it.Hope this helps you guys if I'm not too late.


----------



## phena86

Wow!! So helpful!

So is that 42 ounces of each oil that you use or split them up?


----------



## kmarvel

The more I read these threads on calcs the more confused I get.  Can someone just give me the correct oils for the use of a Pringle Can, Please??  I know that the volume of water it holds is 32 oz.
 Superfatted to 8%.

 I would be so grateful.

 Kathie


----------



## Bubli

kmarvel said:


> The more I read these threads on calcs the more confused I get.  Can someone just give me the correct oils for the use of a Pringle Can, Please??  I know that the volume of water it holds is 32 oz.
> Superfatted to 8%.
> 
> I would be so grateful.
> 
> Kathie



You may want a second opinion, I have never used a Pringles can, but I just looked at that site and from what  math I did, I came up with 24.04 oz of oils which is just shy of 1.5 ponds of oils.  IF WHAT YOU ARE SAYING IS THAT YOU CAN HOLDS 32 oz.  of liquid.

32x1.8=57.6x.40=23.04

Further as an example  take your total.  Your case is let's round to 23, below is what I coppied from the site , his example is 38, just swap your 23 out with his 38 and do the math.See if that helps.  I may be wrong, but I'm good at math and that's what it looked like to me.

35% olive oil
30% coconut oil
30% beef tallow
5% castor oil
Your recipe would be:
13.3 ounces of olive oil (38 X .35)
11.4 ounces of coconut oil (38 X .30)
11.4 ounces of beef tallow (38 X .30)
1.9 ounces of castor oil (38 X .05)

This would give you how much of each of your oils then run that recipe through a calculator.

Also sorry,  replace your oil percentages for the ones in example.  This calculation would also include your water.   AND IF I AM INCORRECT,  SOMEONE PLEASE FELL FREE TO JUMP IN.  I DON'T WANT TO MIS INFORM ANYONE.

Ya know too,  I was just thinking....if you try that calculation, a way to check accuracy first is fill a container with ALL WATER IN PLACE OF ALL INGREDIENTS according to the final calculation and what a soap calc says for lye water amounts.  take your 23 oz oils, plus the water, amount of lye ( but use water not lye), EO's,  milk,  whatever. Use only water in place of each ingredient and  measure by weight,  grams is more accurate but you probable know that.  And see if it fits.  That's actually what I used to do before I came across that math trick.  Just a thought. . Good luck!


----------



## CraftyRedhead

kmarvel said:


> The more I read these threads on calcs the more confused I get.  Can someone just give me the correct oils for the use of a Pringle Can, Please??  I know that the volume of water it holds is 32 oz.
> Superfatted to 8%.
> 
> I would be so grateful.
> 
> Kathie



I also don't have any Pringles cans, but if you can get the dimensions I can plug them in and help.


----------



## DeeAnna

Bubli -- Your approach appears logical, but I want to offer some cautions. First, you cannot substitute water weight directly for oil weight, since oil is less dense than water. 

And be careful of confusing ounces VOLUME vs. ounces weight. Kmarvel said a pringles can contains 32 oz by VOLUME. Kmarvel will need 32 oz of soap batter by VOLUME to fill the can -- there's no arguing that -- but 32 oz vol of soap batter will weigh less than 32 oz wt.

For water, 32 ounces volume happens to weigh approximately 32 oz weight (and 32 mL of water is approx 32 grams), but once you change the liquid to fats, that one-to-one relationship between weight and volume is no longer valid.


----------



## Bubli

Thanks DeeAnna.  Good to know.   that first part of my suggestion was actually from David fisher site and that calculation is pretty spot on. The second suggestion was what I learned myself before I figured out how to do it more accurately with math.  My way was always shy a pinch but to me that was better than being over and wasting.  Both ways work for me, but now that I learned the mathematical way,  that's what I use. The other you can just check with to be sure before making the batch,  it will be a pinch short,  but it gives you a rough idea.  Always worked for me.  Thanks for the numbers,DeeAnna,  I'll add those to my notes.  So much of what I learn is from people like to you guys here.  All these book I paid so much for seem nearly useless at times.


----------



## kmarvel

DeeAnna,  you are so right!!  I made a second batch of Pringles soap and ran it thru the soapcalc just by experimenting with oil weights.  I used 37.5 oz of soap weight before CP cure.  It was perfect.
 I am sorry if I confused anyone here.  It is a learning curve for me and I am learning so much from everyone.
 Kathie


----------



## kmarvel

I made a 12 x 12 2 1/2" wooden mold.  I come up with 144 oz of oil for this 5 lb mold.   Does this sound even close???


----------



## Hazel

I came up with the same total of 144 oz. But that sure does sound like a lot. That's 9 lbs of oil and you say it's a 5 lb mold. I  have a 5 lb mold (according to the manufacturer) which is approx. 3.5 x 2.5 x 18 and I had calculated 63 oz of oil for it. Of course, I always use more because I like to have extra for some individual cavity molds. Hopefully, someone who is better at figuring out how much oil per mold will be able to give a definite answer.


----------



## kmarvel

Hazel,  I had another 5 lb recipe that used about 68 oz.  That sounds like more in the ballpark to me.
 But that formula 12 x 12 x 2.5 x .4    didn't work for me.

 And I am like you, I will use 70 oz of oil and any left over go into yogurt cups for sample soaps or guest soap.   
 We think alike.  haha

 Kathie


----------



## wetshavingproducts

kmarvel said:


> I made a 12 x 12 2 1/2" wooden mold.  I come up with 144 oz of oil for this 5 lb mold.   Does this sound even close???



That cannot possibly be a 5lb mold. You have 1 entire square foot of area and then 2.5" of depth.

That's a volume of 360 cubic inches.

Compare to Hazel's volume of: 157.5 cubic inches.


----------



## kmarvel

Yup, and the  111.3 oz of soap barely fit in the bottom of the mold.  oops.
 I told you I was challenged in math.  hahaha  If anyone could give me the total oz this mold holds, I would be obliged.

 PS,  I got these mold dimensions off of a youtube "how to make a soap mold" video.


----------



## Sprag

I came up with 144 oz according to your measurements. You have a 9 lb mold.


----------



## Sprag

144 oz's divided by 16 = 9lbs


----------



## Hazel

kmarvel said:


> And I am like you, I will use 70 oz of oil and any left over go into yogurt cups for sample soaps or guest soap.
> We think alike.  haha
> 
> Kathie



The excess does make nice guest soaps. Candy molds work great for tiny decorative soap.

Are you going to try another batch with 144 oz of oil?


----------



## kmarvel

I went to Summer Bee calc and put the 12 x 12 x 2.2" in for the oils and came up with 132 oz of oil and total soap before CP cure with 193.5 oz of soap.  Which with the 132 oz of oil comes to an 8 lb mold.   DANG!!!!!!  I made a honkin' soap mold!!!  hahaha

 Live and learn!!!  I quickly (fastest ever) lined a 3 lb mold and repoured my soap in that along with 4 yogurt cups.  haha  I think it will be ok.

Decided to make them 2.2" high instead of 2.5".


----------



## Hazel

At least you _*made *_your own soap mold. I wish I could make my own. Please post pics of this batch and let us know how it turned out.


----------



## kmarvel

Hazel, I will do that!   This weekend it is back to making a "smaller" soap mold. 144 oz of oils sound like a lot to me!!


----------



## LBussy

Hey all ... sorry for bumping this thread but I thought I would share:

[Link no longer functional. Removed by SMF Modmin Team]

This is a spreadsheet that will allow you to figure mold volume in ounces or grams, in rectangular or round molds, with 0.40 or 0.38 factors. For round use the green boxes (H & D), for rectangular fill in L, W and H. If you have any number (including 0) in the D (Diameter) box it will figure the volume of a round container based on that and the height, so be sure to delete that field if you intend to figure rectangular.

I'll try to remember to leave this up and available, but it's on my working DropBox account and could be deleted or moved so snag it now if you want it.


----------



## Hazel

Lee - 

Thanks for sharing! I downloaded it to DB and played with it. My results were just one ounce off (small mold) to 3 ounces off for the 5 lb mold. It could be because I didn't double check the width or it could be because I discount water and have room for more oils. Anyway, it's very helpful and  it's generous of you to share the calculator.


----------



## LBussy

Happy to help.  I can't speak to why these are right, just that *if* the whole 0.40 and 0.38 factors are correct then these are correct.


----------



## Bubli

Stupid question....I am reading conflicting opinions on how to calculate and what the results mean. After reading a few different sites, as best I could gather, when you multiply L X W X D X .40 you get the amount of oils AND water that mold will hold,right?  Or do you have to add your water amount to this total.  I am about to order new molds and wanted as perfect a fit as possible, I found some people that make custom. So is it just the oils or water too? The .40 represents water right?


----------



## LBussy

Not a stupid question Bubli, was wondering the same thing.  I just took a factor that someone else posted and made a spreadsheet.


----------



## scotsman

I may be wrong here, and this may have already been said in an earlier post, but from looking at the formula and comparing it to various base recipes I have, it would seem that the .40 is actually the water % in the recipe, or rather, an approximate. This would explain why it doesn't come out quite right for some. If you use a water % other than 40 then the formula will be off a little bit. So, if I'm correct, and I may not be as math is not my forte, the formula should be as follows:

Length x Width x Depth = Volume

Volume x Water % = Total oil weight for mold

By way of example lets say the interior dimensions of the mold are:

Length=24"/Width=3"/Depth=2"
So...
24 x 3 x 2 = 144 cubic inches volume

If we're using a water % of 40 then:
144 x .40 = 57.6 oz of oils

But now let's say it's your first time making soap and first time using soapcalc so you opt to go with the default 38% water. Your equation is 144 x .38 = 54.72 oz of oils

So that 2% variance in water gives us a variance in total oils of 2.88 oz. not that big of a difference, but let's say you use 33% water for your recipe. Now your equation is:
144 x .33 = 47.52 oz of oils

That gives you a variance of 10.08 oz of oils. This is a significant difference. If you make your recipe with 33% water, but calculate using the standard .40, then you will still have a considerable amount of room left in your mold after you put the batter in it. And this doesn't even account for coloring, fragrance, or additives...though these are usually a much smaller % in most recipes. 

The initial formula with the standard figure of .40 is solid, and will get darn close for most people, but if your recipe calls for a rather steep water discount then you would benefit from recalculating and swapping out the standard .40 for whatever your water % happens to be. 38% water would be .38, 33% water would be .33, etc. 

Again, this is just a theory and I may be way off base with this one. Maybe at some point if I have some spare time and supplies I will do an actual test of this theory and post my findings here. I'm actually rather curious to know for sure. I hope this is helpful.


----------



## coffeetime

Scotsman, if the water amount used is going down from 40% to 33% in your example, wouldn't that mean you need more oils to fill the same volume mold, not less? With less water used, you would want to increase how much batter you are making by the missing water or your mold will be short.

I usually water discount by varying amounts depending on the recipe, and I found I couldn't use that formula at all. I had to trial and error it with that formula as a starting point. Took a couple of batches but not a big deal.


----------



## scotsman

@coffeetime- you're right. I just reread my post. That's what I meant to write. I haven't really slept much the past couple days and got it jumbled around, lol! I guess I should try to go to bed


----------



## LBussy

The formula looks up the value in the header, so once you find out what factor works for you, you can change your personal copy of the spreadsheet and it will work as you intend.


----------



## scotsman

I want to try out that spreadsheet but unfortunately can't do it from my phone. My laptop took a header off the table and it destroyed the screen.


----------



## Hazel

Well, I'm not a math genius but I didn't think I was this bad at math. I went by the amount I calculated for a 5 lb mold and I still ended up with extra soap. It's not a big deal since I like to have extra to make small soaps in individual molds. But I still don't know why my amount is so off. According to the calculator, the mold 18 x 3.5 x 2.5 = 157.5 x .4 = 63 oz. (I should mention this is a new mold. I usually make 2 lb to 2.5 lb batches.  I also don't generally fill the mold all the way to the top so I calculated slightly less which is why my original amount was a few ounces off.) Anyway, I decided to go with the calculated amount based upon the formula of 63 oz + 1 extra oz so I'd have the large loaf and a little extra for one individual soap. Since I used 33% lye concentration, I expected the loaf to be slightly under 2.5" but I was able to fill to the top and ended up 14.7 oz extra soap. Of course, the leftover soap's weight would include water, lye and additives. Still, this is an excessive amount to have left. 

If I calculate using .33, it comes out to 52 oz (rounded off). This actually seems to be a more accurate amount for this size mold. I'm going to try another batch this weekend and use 54 oz to see how full I can get the mold plus possibly have a little left. I'll have to report back after I make it.


----------



## LBussy

You can change this number to adjust for the multiplier that works for you and your process.







Again I was taking for granted that these numbers were correct so if the collective finds out that they are not they can easily be edited.  I have two spots there so you can say "I know somewhere between X and Y works for me" and show that range.


----------



## Hazel

Thank you! I didn't even think of changing it. I decided to double check the size of the mold because I had been using the sizes shown on the site. I thought maybe the mold is slightly smaller than was shown in the description. Nope...measurements were correct.

I'm learning something new. I'd never worried about calculating according to the formula since the small molds I used I had already learned how many ounces of oil I needed. So, I never double checked them based on this formula.


----------



## scotsman

I tried the formula with my small loaf mold that I use for test batches but changed the .40 to .38 because my water is 38% and it filled the mold almost perfectly. I'm going to try another batch using 33% water and use .33 as the multiplier to see if it works. Will post up the results after the test. Keeping my fingers crossed.


----------



## LBussy

Okay I did some more work. The "factors" provided were a pretty close rule of thumb but as folks have noticed not always right. I have done a new spreadsheet that should be much closer AND allows one to tailor the water%.






Here's the spreadsheet - as always please download if you want to keep it because it's possible I move something and break the link at some point.

I don't know how everyone figures water but this assumes water as a % of oil weight as shown on SoapCalc. It also assumes the oil you use weighs 0.033 lb/in^3. "Solid" oils like Lard, Tallow and Shortening weigh 0.031 lb/in^3 but I *think* that's as a solid so using the oil number only should get you very close.

[Link no longer functional. Removed by SMF Modmin Team]

As always, please let me know if you see a glaring mistake.


----------



## scotsman

I really want to download and try out this spreadsheet. **** my laptop for committing suicide. I really need to get a new one.


----------



## LBussy

Scotty, try this.  It *looks like* it works, but I did not really do a bunch of testing:

https://docs.google.com/spreadsheets/d/1tfyAXhFNQGVgncV5QOTaxFJZREzmFfB6wx0HWdf5n_E/edit?usp=sharing


----------



## scotsman

Thank you for the link. I'll have to wait till I get a new comp though because on my iphone it's read-only


----------



## Hazel

Thank you, Lee! I'll have to play with this one.

I did find 54 ounces of oil without a water discount almost filled the 5 lb mold. I was a little disappointed because I wanted some to fill a little dragon mold. I used your new calculator and it came up with 61.77 oz. I'll have to try this amount but it won't be until the weekend.


----------



## Tilia

delicious said:


> I am completely ignorant when it comes to ounces and inches, so I did the math to figure out what it would be in cm and grams.
> 
> Take the volume in cubic cm (Length x Width x Height).
> Divide that by 2,54^3 (which is 2,54 x 2,54 x 2,54) = 16,39 (to get the cubic cm into cubic inches).
> And multiply by 28,35 to convert that into ounces.
> Then multiply by the 0,4.
> 
> So it's:
> (L x W x H) / 16,39 x 28,35 x 0,4
> 
> *Which is the same as :
> (L x W x H) x 0,692
> 
> That's for the metric users.*
> 
> 
> Please note: I have not tested this formula so use at your own risk! Althouth the link given by TopCat http://www.smellychicksonline.com/2008/ ... your-mold/ gives 0,657 for metric users... I don't know where it comes from but it is very close to what I found.



I use metric measurements and everyone seems to agree on something around volume x .7 to calculate the amount of oils needed for a mold. So I tried using that twice now and end up with less soap than needed both times. 

I used a tea-box with 2 compartments today with each compartment measuring 8 x 6.5 x 4.5 cm's. So multiplying those measurements by 2 and then by .692 I ended up with 323 grams of oils needed. While these molds are small I still ended up with the soap being over half a centimeter below the line I wanted it to reach. 

For the recipe I used the standard water amount used in soapcalc of 38%. I that what makes a difference? Not sure on how to factor the water amount in the calculation.


----------



## IrishLass

Yep- the water amount (and any other extra additives included) will have an effect on the level. I don't exactly know how to calculate those variables in, though. I just use the equation as a rough guide and then keep meticulous notes of the actual outcomes and adjust from there.


 IrishLass


----------



## Cactuslily

Idk why I'm still struggling so much! I seem to have a mental block when figuring out what size mold to use for what recipe. For example I made a batch of soap using BB 10" mold. Per calculations, I got 38.5oz. It states on website it holds 50. I'm assuming the recipe given could have had more soap added to mold so that's the differance. If a recipe states it makes a2 lb batch, does that mean I can use my 2.5 mold? Why am I having such a hard time?! I'm feeling my age! Am I overcomplicating this?  L x W x H x .40= ounces of oils needed. This doesn't account for water and additives, correct? I plugged in 50ounces to soap calc ( which is what BB states). My recipe came out with a total of 53.1 ounces not including FO. The original recipe held total of 43.8 ounces. Does that mean my recipe won't fit into a 50 mold? Am I even making sense? Uggh! Probably not.


----------



## Saponista

LxWxHx0.4 is the calculation you would use if you were using full water. So you would do that and the resulting value is the amount of oils you would put into soapcalc with full water to fill your mould. Any other additives on top of that will increase the volume further and overfill the mould. If you are using a water discount then you need to do a different calculation. If you put the amount of fragrance you want to use into soapcalc too, it will take it into account for you I think.


----------



## TrishNZ

Has anyone worked this out in metric?


----------



## Kittish

TrishNZ said:


> Has anyone worked this out in metric?



Post #187 has the weight/volume ratios for water, oils, and solid fats given in both metric and imperial. It's kind of clunky to get there, but with that info, plus the measurements of your mold you should be able to come up with a fairly close answer. 

Also, this is an old thread. Last post before ours were over two years ago (though I'll admit the info in the thread may well be handy to several of us new folks). Necro posting is kind of frowned on, overall. Much better to quote snips from the old thread you're referencing in a new thread.


----------



## TrishNZ

Kittish said:


> Post #187 has the weight/volume ratios for water, oils, and solid fats given in both metric and imperial. It's kind of clunky to get there, but with that info, plus the measurements of your mold you should be able to come up with a fairly close answer.
> 
> Also, this is an old thread. Last post before ours were over two years ago (though I'll admit the info in the thread may well be handy to several of us new folks). Necro posting is kind of frowned on, overall. Much better to quote snips from the old thread you're referencing in a new thread.



Sorry I am new and just using the search feature.  I am not sure what Necro posting is.


----------



## Kittish

Read this post, especially the second part, to learn about necro posting: http://www.soapmakingforum.com/showthread.php?t=56833.


----------



## Steve85569

L x W x H = volume

Trish,

If you calculate in metric (cm) then multiply volume by 0.70 for the weight of oils that will fit.
If you calculate in inches use 0.37 for the weight of oils.

Some corrections will need to happen because of additives but this get me real close.


----------



## SoapAddict415

I realize this thread was started in 2008 but I'm hoping that someone can answer my question. I've seen this formula but with different numbers such as .40, .38 & the last post suggested .37. I don't care which number I use, I can't seem to get the right amount. When I've tried for example  7 * 3.75 * 3.5 * .40= 36.75 ounces (rounded up to 37) as the amount of oils, I end up with a few ounces of too much soap. So, reasoning that the formula calculates volume/how much the mold holds, I've tried creating recipes that have a total weight of 37 oz but I usually end up a few ounces shy of a full mold. Where am I going wrong?


----------



## dibbles

Are you using a water discount? Using that formula, with full water, 31 ounces will fill my mold. At 30% lye concentration, 32 ounces will fill it, with maybe a bitty bit left over.


----------



## SoapAddict415

I usually use full water, 38% and whatever lye concentration that soapcalc gives me. I made this mold & 1 other about 2 years ago & I don't think I've ever been able to correctly calculate how much soap batter I need.


----------



## soaperwoman

I know this may sound dumb but I hate math so all I do is fill my mold with water and then measure that to get my volume. Then I reverse engineer the water amount on a soap calc and oila! It isn't very scientific but it works every time.


----------



## SoapAddict415

soaperwoman said:


> I know this may sound dumb but I hate math so all I do is fill my mold with water and then measure that to get my volume. Then I reverse engineer the water amount on a soap calc and oila! It isn't very scientific but it works every time.


I've done that with my silicone molds but this is a homemade wooden mold. It's not going to hold water.


----------



## dibbles

Why don't you purposely make a little too much batter with your regular recipe/water amount and weigh what is left when your mold is full?


----------



## Millie

SoapAddict415 said:


> I've done that with my silicone molds but this is a homemade wooden mold. It's not going to hold water.


If you are having good luck using that method, could you line your mold with a garbage bag for your water measurement?


----------



## SoapAddict415

I hadn't thought of that. Thank you, it's worth a try.


----------



## Zany_in_CO

Have you tried Summer Bee Meadows Recipe Resizer?

http://summerbeemeadow.com/sites/all/cgi-bin/sbm_lye_calculator_1.1.cgi


----------



## SoapAddict415

Zany_in_CO said:


> Have you tried Summer Bee Meadows Recipe Resizer?
> 
> http://summerbeemeadow.com/sites/all/cgi-bin/sbm_lye_calculator_1.1.cgi


 never heard of it but I'm looking forward to giving it a try! Thanks!

Sent from my Z828 using Soap Making mobile app


----------



## Zany_in_CO

SoapAddict415 said:


> never heard of it but I'm looking forward to giving it a try! Thanks!


I just checked it. It looks like you have to go to the calculator first in order to get to the "resizer" on the next page, where you can then type in the measurements of your mold and it gives you the amount of oil needed for that mold.

http://summerbeemeadow.com/sites/all/sbm_calc_input/calc_input_page_1.1.html

HTH


----------



## SoapAddict415

Zany_in_CO said:


> I just checked it. It looks like you have to go to the calculator first in order to get to the "resizer" on the next page, where you can then type in the measurements of your mold and it gives you the amount of oil needed for that mold.
> 
> http://summerbeemeadow.com/sites/all/sbm_calc_input/calc_input_page_1.1.html
> 
> HTH


Thanks. I was trying to figure it out but I didn't get far. I'll try again after work tonight.


----------



## cwayneu

IanT said:


> hey paul, thanks for the helpful thread!!..
> 
> 
> just curious, where does the .40 come from??


The .4 is actually an approximate conversion factor of any volume in cubic inches, to ounces of oils for that volume of soap. The total ounces will be the oils plus the lye and water, but Soapcalc will tell you this exactly, depending on things like superfatting and lye/water ratio. Some chemist probably figured this out way back when.


----------



## SaltedFig

Sorry, but in metric that linked calculator has major flaws.



Zany_in_CO said:


> ...


----------



## Zany_in_CO

SaltedFig said:


> Sorry, but in metric that linked calculator has major flaws.



??? Do you mean this one:



Zany_in_CO said:


> I just checked it. It looks like you have to go  to the calculator first in order to get to the "resizer" on the next  page, where you can then type in the measurements of your mold and it  gives you the amount of oil needed for that mold.
> 
> http://summerbeemeadow.com/sites/all/sbm_calc_input/calc_input_page_1.1.html


----------



## Saranac

SoapAddict415 said:


> I realize this thread was started in 2008 but I'm hoping that someone can answer my question. I've seen this formula but with different numbers such as .40, .38 & the last post suggested .37. I don't care which number I use, I can't seem to get the right amount. When I've tried for example  7 * 3.75 * 3.5 * .40= 36.75 ounces (rounded up to 37) as the amount of oils, I end up with a few ounces of too much soap. So, reasoning that the formula calculates volume/how much the mold holds, I've tried creating recipes that have a total weight of 37 oz but I usually end up a few ounces shy of a full mold. Where am I going wrong?



There are too many variables to successfully use another person's (or calculator's) conversion factor (especially if you don't want too little or too much); you need to calculate your own.  This is how I handle this type of situation:

My current recipe yields bars that are 2.5 inches tall.  Now assume that I want to increase their height to 3 inches.  My conversion factor is:

New Height / Old Height

For my example above:

3 / 2.5 = 1.2

I would then scale my formula up by multiplying the weight of EVERYTHING in my formula by that number.

This also works if you want to make smaller bars.  Lets say I want to scale my formula down, so that my 2.5 inch tall bars are only 1.5 inch:

1.5 / 2.5 = 0.6

I could then scale my formula down by multiplying the weight of EVERYTHING in my formula by that number.


----------



## SaltedFig

Yes (sorry, I thought that clinking the link in my post would take you directly to your post ... it worked when I tried it. Thanks for letting me know it's not helpful!).

Test by using *grams*, enter 1000grams of olive oil at 10% superfat, and *resize* to a soap bar measuring 2cm high by 5cm long by 3cm wide. See how many grams of oil it says you need.



Zany_in_CO said:


> ??? Do you mean this one:



*Measuring mold volume without maths*

*Using salt to get the volume of your mold (and avoid all volume maths!):*

Pour salt into your desired mold, then pour the salt from the mold into a measuring jug. Read volume.


To use the multiplier from this thread (thank you!) to work out the weight of oil needed for your recipe.

For metric, multiply your volume by 0.7
For imperial, multiply your volume by 0.4

You will need to fine-tune this multiplier to suit your own recipe (as it varies with different lye strengths, additives, oils etc.)
(so in Steve's example below, his multiplier is accurate at 0.37)


*To resize your recipe to fit a new mold:*

Pour salt into your existing mold, then measure the volume of the salt. Note the volume.
Pour salt into your new mold, then measure the volume of the salt from the new mold. Note the new mold volume.

Divide your new mold volume by your old mold volume. This is your Resizer Value.

Multiply your Resizer Value by the total oil weight of your original recipe.

The answer given is the total weight of oil you need for your new mold.

In one calculation this becomes New Volume / Old Volume * Original Weight = New Weight

1/ The Resizer Value will work just as well to calculate recipe weight (by multiplying the Resizer Value by your recipe weight, instead of oil weight)

2/ The Resizer Value will work using any weight measurement (eg. grams, kilos, pounds, ounces ...)

3/ You can substitute any pourable solid for the salt. So you can use salt, rice, split peas, sand ... whatever, so long as you can pour it.


Steve's example:


Steve85569 said:


> L x W x H = volume
> 
> Trish,
> 
> If you calculate in metric (cm) then multiply volume by 0.70 for the weight of oils that will fit.
> If you calculate in inches use 0.37 for the weight of oils.
> 
> Some corrections will need to happen because of additives but this get me real close.


----------



## Saipan

Metric?  What the hell is that?

Just remember we put men on the moon with good ol Imperial measurements.


----------



## LBussy

Saipan said:


> Metric?  What the hell is that?
> 
> Just remember we put men on the moon with good ol Imperial measurements.


Didn't we also screw up some mission or other trying to convert between the two?

I sure like math using metric measurements better, but I still don't know what to expect out of C ... like, what's comfortable?  I know 70F is fine but remembering 21C is comfortable eludes me most times.


----------



## Zany_in_CO

Saipan said:


> Just remember we put men on the moon with good ol Imperial measurements.



You're joking, right? Um, in architecture & engineering, we use mostly metric -- just like soapers prefer to use grams for lotions & potions. I s'pose NASA did too. The interesting thing back then is, when JFK was elected President of the USA, he promised we would land on the moon in 10 years. He also promised that, in those same in 10 years, we would be on the metric system! Maybe that's why he was assassinated?! (Just kidding.) 

Americans are resistant to change, even if it's good for us. I'm embarrassed that we are the only "civilized" country in the world that still uses the Imperial system. Sad really and, dare I say, ignorant... in a nice way of course.


----------



## LBussy

I thought Great Britain used Imperial measures for a lot of things?


----------



## The Efficacious Gentleman

Not always, mostly not anymore. Miles still, not km. Cm or mm mostly, but a lot of people still think in inches. Height, for example. Weight for people is stone. Cooking is mostly grams  It's an odd mix, that is for sure. 

Actually, zany, NASA did use a lot of Imperial at that time. Even the lunar module coming down was measuring the distance to landing in feet


----------



## Saponista

Yes I am weird, I only know my height in ft and ins, and distance in miles but I measure everything else in metric. I weight myself in stone and lbs, but I weigh everything else in metric. We do a weird sort of hybrid lol


----------



## Dahila

Mile is difficult for me even I know it is 1600 m,  inch is weird it has a tiny bit less that 2.5 cm,   I am metric and took me a long time to get ounces  Thanks heaven we use Km and litres in Canada, there is always also imperial measurement on most things but will be on the second place ie 1000 g /2.2 lb


----------



## Saipan

I was joking, yes, but I do like to point that fact out.  The UK uses Imperial for a good many things still, I do blacksmithing, and often things are still Imperial for that in the UK.


----------



## iwannasoap

I tried this with the recipe I just made yesterday. I figured .40 stood for 40% of oils. I was definitely wrong about that one but I compared it to what I did yesterday because I only lost 2.46% (and I was scraping the bowl) so It was pretty close to use it as an example.
Anyway, doing this for the same mold I used yesterday works better for me if I used .42 instead of .40. If I would have done this yesterday I would have lost less then 2.46% because that would have put me a little more then a 1/4 oz closer to my target. 
To make it short, .42 works much better and is closer to the top of the mold in my opinion. I'm like the other guy here, "What is .40?"


----------



## The Efficacious Gentleman

Maybe in some instances .38 is better, too, so they had to find an average which is near enough all of the time, but unlikely to be perfect every time. 

At least thanks to whoever worked it out first time round, you had a ball park figure to start with, even if they didn't make it totally perfect for your particular batch of soap


----------



## DeeAnna

Here's more background on this topic -- http://www.soapmakingforum.com/showthread.php?t=58581

"...As you all have been sharing in this thread, some soapers will end up with too much batter from using the 0.40 rule, and some won't have enough. So it's obvious the 0.4 rule is simply a rough rule of thumb. Whether the original person originally came up with this number empirically or by calculation, it really doesn't matter anymore. What does matter is the 0.40 rule has been around for some years now and soapers are still using this rule of thumb, so it is proving to be reasonably helpful for most people most of the time, despite its limitations...." --DeeAnna


----------



## isha

I use imperial system...  Weighing. In grams 
So this is what I've learnt and used..  Works well
You need to calculate the size of mould in cms.  Instead of inches and multiply by the std multiplier 0. 72
So now calculate (in cms) 

 VOLUME =L X B X H
 Weight of oils = V X 0.72 (GRAMS)

for pvc of round mould. ( IN CMS) 
V= pi X R X R X H

Weight of oils (grams)  = V X 0.72


----------



## Garnet_Tree

*Ounces of Oils*

These formulas work for OUNCES of oils. 

If you want to work in grams then you need to do the calculations and then convert to grams. Many soap calculators do this for us. There are approximately 28.35 grams in 1 ounce. 

To make the conversion, multiply length (in inches) x width x height x .4 x 28.35 to get the grams of oil needed.


----------



## isha

@ garnet tree..  I've  mentioned a simpler  version of this.  Hope it helps [emoji4]


----------



## SaltedFig

I think mzz said it most clearly in 2012, with this:



mzz said:


> For metric I use:
> Volume (cm3) x 0.7 = ? g oils



So,
Imperial, use 0.4
Metric, use 0.7

Like all general rules, this one needs to be adjusted for your personal recipe.

For anyone who would like to avoid doing volume math, this link is to a straightforward volume calculator for cubic and cylindrical molds (just plug in your measurements in imperial or metric, and it will give you the volume): http://www.ifocas.org/calculator.htm


----------



## isha

Thanks saltfig..  That went on my bookmark immediately..  U saved a ton of brain scratching time for me


----------



## rjuconnfan

Good info..exactly what I needed to know for my first soap. I have no idea how many molds to have ready to go when I start mixing.....I don't want to be running all over trying to find things. I only have a couple small loaf style to start but will make up a few from recycled milk containers etc. Just in case! Thanks for the post.


----------



## AnnaBanana

12 pages!  
So I’m new to soaping.  Only made one batch so far.   Got myself off kilter using the measurements of the mold, cubed x .40, because I was a bit befuddled where the lye water fits into that calculation.  Using the calculations I got the oz of oils for a 3.5 lb.  After adding in the lye water, I now had almost 5 lbs of soap not 3.5 lbs.  Luckily I had a small plastic tub for the extra.   How does the lye water factor into the calculation.  That water takes up volume too.


----------



## DeeAnna

Yes, you are right -- the lye solution takes up space too. The 0.40 estimate allows room for the water part as well as the oil part, so you don't have to deal with the lye solution volume.

Remember, however, that the 0.40 estimate is an estimate, not a surefire number that works exactly right all the time. The 0.40 number is based on assumptions about the proportions of water, NaOH, and fat that make up a typical batch of soap. The actual volume of YOUR soap may be different depending on how you design your recipe. Do you use more water than is typical? Did you include bulky additives? How much fragrance did you use? Etc. (See also Post 229 in this thread.)

Some people use 0.38 instead of 0.40 to estimate the recipe size for their mold, because they find the 0.40 number overestimates the volume of soap they need. Others might use 0.42.

Now that you know how much extra soap you made, you can tweak the amount of fats for your recipe until the batch fits your mold without any excess, if that's what you want to do. Some people like to make a little extra batter, so they can fill a few guest-sized soap molds as well as fill their main mold.


----------



## John Harris

Soapmaker Man said:


> Hi everyone.I wanted to post this as a sticky so all could learn how much oils are needed for your mold.  Here is the way to figure it.
> 
> Lets use a log mold that is 12 inches long, 3-1/2 inches wide, and you want to pour to a depth of 2-1/2 inches.
> 
> You take length X width X height of pour, that number X .40.  So;
> 
> 12 X
> 3.5=
> 42
> 
> 42X
> 2.5=
> 105
> 
> 105X
> .40=
> *42 ounces of oils needed for this mold.*
> 
> Apply these same numbers for your mold size, weather a log, slab, or block. :wink:
> 
> Paul



Does this work using centimeters?


----------



## DeeAnna

John Harris said:


> Does this work using centimeters?



No. The 0.40 factor is for inches and weight ounces. Use 0.70 for centimeters and grams. You're on your own if you use any other combination of units.

I show the math to derive both rules (0.40 and 0.70) in this article -- https://classicbells.com/soap/moldBatchSize.asp


----------



## Kosmerta

Soapmaker Man said:


> Hi everyone.I wanted to post this as a sticky so all could learn how much oils are needed for your mold.  Here is the way to figure it.
> 
> Lets use a log mold that is 12 inches long, 3-1/2 inches wide, and you want to pour to a depth of 2-1/2 inches.
> 
> You take length X width X height of pour, that number X .40.  So;
> 
> 12 X
> 3.5=
> 42
> 
> 42X
> 2.5=
> 105
> 
> 105X
> .40=
> *42 ounces of oils needed for this mold.*
> 
> Apply these same numbers for your mold size, weather a log, slab, or block. :wink:
> 
> Paul



If only I had seen this post 12 hours sooner. I measured my mold in cm, calculated ml from there and converted ml to oz. My batch was allllmost perfect for my mold, but I had about 2.5 oz of extra batter. I had to rush an find my 4 oz cube mold from my supply area for the excess!


----------



## KDP

Thank you for this, Paul! My son asked what I wanted for Christmas....please build me a slab mold..I've been researching for directions/instructions. This is perfect! Thanks!


----------



## LaPrairieLady

I put the water in a measuring cup and count the ounces until my mold is full. I know that 1 pound of soap is 16 ounces oil + 6 ounces water + 2.23 ounces lye give exactly 3 cups of batter (24 ounces) I mix in my pyrex 4 cups.


----------



## lshone

DeeAnna said:


> No. The 0.40 factor is for inches and weight ounces. Use 0.70 for centimeters and grams. You're on your own if you use any other combination of units.
> 
> I show the math to derive both rules (0.40 and 0.70) in this article -- https://classicbells.com/soap/moldBatchSize.asp



I setup a spreadsheet to work out the volume of oil based on the ClassicBells link.  My original goal was to create a 4oz bar, so this spreadsheet kinda evolved from that. I use loaf molds so the spreadsheet is setup for any type of L x W x H volume calc. 

I've reworked the example from the ClassicBells link provided, but set the superfat and FO values to zero. When I use a 33% lye conc. I get a .7 conversion factor almost exactly. 

I've added the conversion factor to the spreadsheet so I can see how it changes with the lye concentration. It's more out of curiosity now, as the spreadsheet calculates what I need. I let the spreadsheet do the work, then I run everything through soapcalc or soapmakingfriend to get a nice print out of the recipe.

Here is a link to the spreadsheet I use ==> CP Soap Resizer

The cells with the orange border are where I "input" data that needs to be changed, based on whatever formula I'm using and whatever mold size I'm working with. This spreadsheet works with lye concentrations between 20 and 50. The "blue" cell gets its value from the lookup table in sheet2, based on input % lye concentration.

I got the lye density values here ==> Handymath.com
The oil densities I just found on the internet. 99% of the time a value of .92 is close enough.


----------



## Kosmerta

I'm still slightly confused about the 0.4 rule. This post says AreaX0.4= weight of oils. Does this mean total weight of batter of JUST the oils? Once my lye water is added my batter would be a larger volume than just the oils clculated by the 0.4 rule.

Is the rule already claculated to include lye solution? If so, what concentration? I like to make my lye at 33% using 2:1 water: NaOH.


----------



## DeeAnna

_"...This post says AreaX0.4= weight of oils...."_

It's VOLUME X 0.4 = weight of oils.

_"...Does this mean total weight of batter of JUST the oils?..."_

The answer you get from the 0.4 Rule for inches and ounces (or the 0.7 Rule for centimeters and grams) is _just _the weight of _oils_.

_"...Is the rule already claculated to include lye solution? If so, what concentration? I like to make my lye at 33% using 2:1 water: NaOH...."_

The number 0.4 is there to account for the volume of the water and NaOH. It's based on the assumption of using a 28% lye concentration. It's also based on assumptions about the particular fats in the batch. It's not just the lye concentration that affects the batch volume.

If you use a higher lye concentration, that will reduce the volume of batter slightly. If you use more coconut oil or other fats with high saponification values, the volume of batter will be slightly less. If your batch includes fragrance or any other additives, the batch volume will be slightly higher.

This Rule is a quick and easy way to estimate how bit of a batch to make when using a new mold for the first time. It's not ever going to be perfectly accurate for all soap recipes all of the time. I know a more complicated method could be created to nail down the answer within a narrower margin of error, but honestly most soap makers are really looking for quick answers that require minimal math and measuring. That's what this Rule accomplishes.

I discuss the assumptions used in the 0.4 Rule in my article here: https://classicbells.com/soap/moldBatchSize.asp


----------



## Brokinkiy

I just got a small mold for sample bars and this is just what I needed. I wish I had looked at it before I made my large batches. Great info, Thanks Paul!


----------



## Masterok

Where does the .40 come from ? That might be a percentage of volume. So in a typical recipe of soap is 40 percent of the volume from oils?


----------



## DeeAnna

_"...That might be a percentage of volume. So in a typical recipe of soap is 40 percent of the volume from oils?..."_

@Masterok -- Good thought, but not really on-target. See the last paragraph in my last post #237 for a link that answers your question.


----------



## Todd Ziegler

millyb60 said:


> *..*
> 
> Just one question .. when the M&P base is in blocks, how do you know how much to melt to get the "liquid amount"? I hope that makes sense.. for example, say my mould held 100ml of water, how much solid block soap do i need to weigh out in order to have 100ml of melted soap? One would assume around 100g, but i dont know...
> 
> That may have a really easy and "commonsense" answer, but times when i've used this method, ie measuring how much water the mould can hold, i've not been totally successful, had a bit too much most of time..
> 
> Thanks very much everyone  would really appreciate an answer for this


I used a wilton shot glass mold and it used 539 grams of M&P soap. I know that isn't exactly the answer you were looking for but if you look up the mold on line, you can work backwards maybe. I am not good with the math or I would tell you more lol.


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## Wyndham Dennison

weigh  cu inch of M&P. a cu inch of water weighs about 16 grams. 100 gram(ml) water  / 16 =6.25 cu in (x) the weight of m&p should get close or I've messed up the math


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## shunt2011

Todd Ziegler said:


> I used a wilton shot glass mold and it used 539 grams of M&P soap. I know that isn't exactly the answer you were looking for but if you look up the mold on line, you can work backwards maybe. I am not good with the math or I would tell you more lol.


This poster you quoted hasn’t been here since 2008.


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## Wyndham Dennison

oops, hope it helps someone down the line


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## JakeBlanton

LBussy said:


> I thought Great Britain used Imperial measures for a lot of things?



The UK uses metric for certain things and Imperial for others.  Their Imperial system is not the same as the US customary system though.  For example, an Imperial pint of beer is 20 Imperial oz, but their ounces are slightly smaller than US ounces, so if you convert it to US ounces, you around 19.2152 US oz per Imperial pint.  Beer must be sold in pubs in Imperial Ounces, so that is a plus.

35.19508 Imperial Ounces per liter
33.814023 US Ounces per liter

You will find over there that distances between cities on the highway are measured in miles, the distance to an exit that is fairly close is measured in yards, but the clearances of the bridges are measured in meters.

So, when you see a car over there advertised as getting a certain mpg and wonder why the same exact car in the US gets worse gas mileage, you have to remember that their gallons are larger, thus the vehicle can go further on their gallon than it can on the US gallon.

As an engineer, I can use metric, US customary, or even Imperial if necessary.  Depending upon what I'm doing, I'll use what is most convenient to use. 

I think that some people who have trouble with mold volumes are failing to understand densities of the various ingredients and they might also not know that the US ounce (volume) is not the same as the US ounce (weight) even for water.  In the metric system, *originally*, 1 kg *was* defined as 1 liter of water.  Currently, it's defined as:

"The kilogram, symbol kg, is the SI unit of mass. It is defined by taking the fixed numerical value of the Planck constant h to be 6.62607015×10−34 when expressed in the unit J⋅s, which is equal to kg⋅m2⋅s−1, where the metre and the second are defined in terms of c and Δ_ν_Cs."

https://en.wikipedia.org/wiki/Kilogram#Definition

Not exactly something that you can do in your home lab, but it's within 30 ppm of the original definition, so we can get away with the 1 ml = 1 gram of water approximation.

The difference between dry and liquid measurements in the US can get confusing since many suppliers of products do not necessarily state whether it is a dry or liquid measurement that their product is sold in.  Sometimes oils are sold by the liquid gallons and sometimes by pounds.

1 dry gallon = 268.8025 cu-in = 4404.883771 ml
1 fluid gallon = 231 cu-in = 3785.411784 ml

Also, we need to remember that even the rough figure of 1 g = 1 ml of water is assuming that the water is pure and at it's maximum density (approximately 4C).  Most other things that go into these soap recipes have their stated densities at a different temperature.  For example, soybean oil might be 0.9193 g/ml at 75F, but it is 0.9023 g/ml at 120F and 0.8615 g/ml at 230F.

https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1016&context=chemeng_biomaterials

So, for me at least, I would use the metric system for any sort of recipe where the measurements needed to be critical.  That way, you only need to convert the size of your mold from inches to cm (1 inch = 2.54 cm *exactly*).  Of course, this is assuming that you have a scale that measures in grams.



Wyndham Dennison said:


> oops, hope it helps someone down the line



That is my view also.  There are some people who are rather anal-retentive about posting to old threads and think that you should start a new thread.  I disagree with this since I find it more convenient for everything to be in one place than possibly in 20 different threads which are often repeating stuff that was in the other threads.

Unlike many people who are on this forum or on the various YouTube channels about soap making, I have no desire to turn it into a commercial endeavor.  I'm doing it so that I can get a use out of some of my older used fry oil instead of just mixing it with my dogs' dry dog food (they really like it though).  Plus, I want to be able to create a mechanic's soap that is ever better than the Lava brand.  Instead of pumice, I'm thinking of using aluminum oxide blast media.  No fancy fragrances, just basic soap that will clean grease off my hands after I've been working on something in my workshop.


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## linne1gi

I don’t know what aluminum oxide blast media is but I do know that you cannot mix soap with aluminum (the reaction between NaOH and aluminum produces hydrogen gas).


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## JakeBlanton

linne1gi said:


> I don’t know what aluminum oxide blast media is but I do know that you cannot mix soap with aluminum (the reaction between NaOH and aluminum produces hydrogen gas).



Used in "sand" blasting to remove rust or whatever from the surface of a part.  Depending upon what the part is made from, there are various types of media that could be used.  For softer metals, you might use ground corn cob or baking soda.

Since this would be mixed in at the end of the hot process cooking, just before pouring into the mold, I would think that there would be little (if any) lye left to react with aluminum.  Whether lye will even react with aluminum oxide is probably something that I should test, just for curiosity's sake though.

EDITED:

Doing a quick web search, I came up with this:

https://chemiday.com/en/reaction/3-1-0-208

Looks like as long as you keep the temperature below 900C, you don't have anything to worry about.  I'm pretty sure my crock pot won't go that high.


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## linne1gi

My concern also is that soap doesn’t mix well with any metals. That’s why we use distilled water, so as not to have any trace metals in the soap. Metals in soap promote DOS. Dreaded orange spots. Obviously it’s your soap, you do what you wish. But I advise against it.


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## shunt2011

Adding any kind of metal would absolutely enhance the possibility of it going rancid much much quicker.   Even metals in tap water can cause it.


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## I made this soap

Hey! I'm new here and have been struggling with this calculation for a long time now! Thank you


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## SpaceCorgi94

I'm not sure if I somehow missed it (sorry if I did) but is anyone aware of a way of doing this entirely in Metric? (using ml for the mould volume and grams of oil?)

Because all my units here in Metric here in Australia, I've found that trying to constantly go back and forth between converting from Imperial, not only is it difficult, but I've also unfortunately had this calculation work out badly for me during an attempt to make one of my soaps


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## linne1gi

SpaceCorgi94 said:


> I'm not sure if I somehow missed it (sorry if I did) but is anyone aware of a way of doing this entirely in Metric? (using ml for the mould volume and grams of oil?)
> 
> Because all my units here in Metric here in Australia, I've found that trying to constantly go back and forth between converting from Imperial, not only is it difficult, but I've also unfortunately had this calculation work out badly for me during an attempt to make one of my soaps


I think it’s height times width times depth times .08 for metric. Multiply times .04 for ounces.  But I am not positive. Here’s an article I have about it. https://l.facebook.com/l.php?u=http...LMP974-Z1DIMOd5u9bm9wLQB4gLZ4wyA8IB-YxR_r&s=1


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## lshone

SpaceCorgi94 said:


> I'm not sure if I somehow missed it (sorry if I did) but is anyone aware of a way of doing this entirely in Metric? (using ml for the mould volume and grams of oil?)



Metic volume is measured centimeters. Length x width x height = cm3. (one ml = one cm3) The conversion factor between cm3 and cubic inches (ci) is .578.

If the oil (oz) to volume (ci)  ratio is .7 (imperial) then multiply .70 oz/ci * .578  = .40 grams/cm3 (metric).

.7 is the mythical ratio given out by all over the internet. Lye concentration and superfat ratios will change this number. Attached is a table of oil to volume ratio for various lye concentration and superfat values. This should get you pretty close.


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## Soapydaze

Soapmaker Man said:


> Hi everyone.I wanted to post this as a sticky so all could learn how much oils are needed for your mold.  Here is the way to figure it.
> 
> Lets use a log mold that is 12 inches long, 3-1/2 inches wide, and you want to pour to a depth of 2-1/2 inches.
> 
> You take length X width X height of pour, that number X .40.  So;
> 
> 12 X
> 3.5=
> 42
> 
> 42X
> 2.5=
> 105
> 
> 105X
> .40=
> *42 ounces of oils needed for this mold.*
> 
> Apply these same numbers for your mold size, weather a log, slab, or block.
> 
> Paul


Thanks Paul,,,, happy Monday soapmaker


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## Zany_in_CO

Soapmaker Man said:


> Hi everyone.I wanted to post this as a sticky so all could learn how much oils are needed for your mold.  Here is the way to figure it.


Great information, Paul and I agree, it should be a sticky!

Or you can do what I do. I use *Summer Bee Meadows Soap Calc & Recipe Resizer* that allows me to enter the dimensions of my mold on the next page after I've done the calculation. This is especially useful for the math-challenged like me.


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## shunt2011

Zany_in_CO said:


> Great information, Paul and I agree, it should be a sticky!
> 
> Or you can do what I do. I use *Summer Bee Meadows Soap Calc & Recipe Resizer* that allows me to enter the dimensions of my mold on the next page after I've done the calculation. This is especially useful for the math-challenged like me.


He hasn’t been here in 10 years.


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## Zany_in_CO

shunt2011 said:


> He hasn’t been here in 10 years.


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## Steve85569

Hasn't been here in a long time but the information he left behind helped me - many years ago.


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## Something witty

MetalSubstance said:


> P.S. -- one way to figure out the volume of the mold is to fill it all the way with water, then pour the water into a measuring cup.  Then, simply multiply the amount of water in the cup with .40 to get the amount of oil to use.



This probably works well for novelty shapes too (inbeds and more). You can weigh it in your preferred measure unit then mark it on the bottom of the mold for future reference. 
Very helpful thank you


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## Something witty

millyb60 said:


> *..*
> 
> Just one question .. when the M&P base is in blocks, how do you know how much to melt to get the "liquid amount"? I hope that makes sense.. for example, say my mould held 100ml of water, how much solid block soap do i need to weigh out in order to have 100ml of melted soap? One would assume around 100g, but i dont know...
> 
> That may have a really easy and "commonsense" answer, but times when i've used this method, ie measuring how much water the mould can hold, i've not been totally successful, had a bit too much most of time..
> 
> Thanks very much everyone  would really appreciate an answer for this



After I use a mold for the first time I take the results and put it back on the scale to get the total weight. Then mark the bottom with a permanent marker for the future. 
Hope that helps


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## JazzKitten

IanT said:


> hey paul, thanks for the helpful thread!!..
> 
> 
> just curious, where does the .40 come from??


It will be to do with the density of oil. For instance, 1 cubic metre of water weighs one tonne, 1 litre of water weighs one kilogramme. So the volume calculation that Paul has given has the volume of the mould multiplied by 0.4 because I oil is heavier than water - also it's given in inches so that constant of 0.4 will account for the weight conversion to ounces.


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## earlene

One caveat:  In spite of this standardized conversion formula for determining how much oil to use when making soap batter to fit into a specific mold, it does not take into account any variables for lye concentration, which can alter the amount of water (or water replacement), which in turn will alter the total batch weight (and density or volume) of your raw soap.  Nor does it take into account additional additives and their density, as when one adds pumice or salt, etc. to the batter.  All these sorts of things will alter the final total density of your soap and it may be a greater or lesser volume than will fit your mold to the particular depth you thought it would, remembering that neither volume nor density are the same thing as weight.

And there is one other factor that alters density of a substance, and that is heat.  Heat causes many substances to expand, including soap, so the same recipe may produce a larger volume when hot than when cold.

Not to burst anyone's bubble about a tried-&-true formula for determining how much oil to use when altering a soap formula to fit a particular mold.  But as many a soaper has discovered, sometimes the formula doesn't always produce the amount of batter we thought would fit the mold perfectly and sometimes it falls short, while other times we need a back-up mold to put the extra batter into, such as an individual mold or two.


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## stephswan

Hi all, a little late to the game, and I probably should just start a new thread, but I found the formulas in this thread helpful, so just want to double check I'm doing the math correctly for my individual silicone molds:

I have a cloud mold (12 in total), so i poured water in 1 and got: 2.2 fl oz.
2.2 FL oz x 12 (number of molds) = 26.4 fl. oz 
Then 26.4 x .554 (to transfer into cub in) = 14.63
14.63 x .4 (the magic number of calcing oils) = 5.85 oz of oil needed for this mold

this is math correct? just seems like such a small bit of oil.


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## SoapDaddy70

stephswan said:


> Hi all, a little late to the game, and I probably should just start a new thread, but I found the formulas in this thread helpful, so just want to double check I'm doing the math correctly for my individual silicone molds:
> 
> I have a cloud mold (12 in total), so i poured water in 1 and got: 2.2 fl oz.
> 2.2 FL oz x 12 (number of molds) = 26.4 fl. oz
> Then 26.4 x .554 (to transfer into cub in) = 14.63
> 14.63 x .4 (the magic number of calcing oils) = 5.85 oz of oil needed for this mold
> 
> this is math correct? just seems like such a small bit of oil.


I do not think your second equation is correct. Once you get the total volume in fluid ounces you should be multiplying that number by 1.8 to get your cubic inches and then multiply by the .4. So it would be.
26.4 x 1.8 = 47.52 cubic inches
47.52 x .4 = 19 oz of oil needed


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## stephswan

SoapDaddy70 said:


> I do not think your second equation is correct. Once you get the total volume in fluid ounces you should be multiplying that number by 1.8 to get your cubic inches and then multiply by the .4. So it would be.
> 26.4 x 1.8 = 47.52 cubic inches
> 47.52 x .4 = 19 oz of oil needed


THANK YOU!!! I was thinking the final oils looked way too light.


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## AAShillito

Thank you! This is super helpful!


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## ameliashawn

Multiply the number of fluid ounces of water by 1.8 to get the total cubic inches of the mold. For example, if your mold holds 12 ounces of water, 12 X 1.8 = 21.6 cubic inches. 21.6 cubic inches in the mold X 0.4 = 8.64 ounces of oils in that recipe.


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## Spice

Soapmaker Man said:


> Hi everyone.I wanted to post this as a sticky so all could learn how much oils are needed for your mold.  Here is the way to figure it.
> 
> Lets use a log mold that is 12 inches long, 3-1/2 inches wide, and you want to pour to a depth of 2-1/2 inches.
> 
> You take length X width X height of pour, that number X .40.  So;
> 
> 12 X
> 3.5=
> 42
> 
> 42X
> 2.5=
> 105
> 
> 105X
> .40=
> *42 ounces of oils needed for this mold.*
> 
> Apply these same numbers for your mold size, weather a log, slab, or block.
> 
> Paul


is the .40 the %of lye?


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## lshone

Spice said:


> is the .40 the %of lye?


No. The .40 is ratio of the weight of oil to cubic inches, for 1 cubic inch.

Multiply the volume of your mold, measured in cubic inches, by .40 to get the weight of oil required for your mold.

Keep in mind that the .40 is an approximation, so you will need to experiment with  amount for your mold and receipe, and adjust up or down as required.


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