You have to figure percentages from your recipe. For example:
A recipe you find has the following:
Olive Oil - 25 oz.
Coconut Oil - 10 oz.
Palm Oil - 10 oz.
Shea Butter - 5 oz.
Ignore lye and water amounts, because if you scale this recipe up or down, you will require different amounts of lye and water.
Your total oils are 50 oz. To find your percentages, divide each oil weight by the total weight. So...
Olive oil = 25/50 = .50 = 50%
Coconut oil = 10/50 = .20 = 20%
Palm oil = 10/50 = .20 = 20%
Shea butter = 5/50 = .10 = 10%
Then take these percentages and plug them into soap calc with a new total weight, or do it the old fashioned way:
You want a total of 30 oz for your new recipe, so multiply each oil's percentage by 30 oz.
Olive oil = 50% x 30 oz = 15 oz.
Coconut oil = 20% x 30 oz = 6 oz.
Palm oil = 20% x 30 oz = 6 oz.
Shea butter = 10% x 30 oz = 3 oz.
You can then use these numbers to use a simpler
soap calculator like mms.
Sorry if this is all confusing, its hard to explain over the internet!