Lotion Recipe Question

[Luckyone80]

If I were to make a lotion recipe that didn't originally call for a preservative but I wanted to add one like NeoDefend, how would I figure the amount?
I'm not necessarily going to use this recipe but using it as an example:

1/2 Cup Cocoa Butter
1/2 Cup Shea Butter
1/2 Cup Coconut Oil
1/2 Cup Olive Oil
1 Tbsp Vitamin E oil

 

[lsg]

What you have will be more like a butter than a lotion. Lotion contains about 60%-70% water or hydrosol. First you new to weigh all of your ingredients and multiply the total weight by the recommended percentage of preservative.