Calculating mold/recipe size

by Janice
(West Virginia)

I am having trouble calculating the size of a recipe vs the mold. I did your basic soap recipe today.

I like to make large batches because I have 3 daughters who LOVE my soap and I send them many bars.

I used your calculator with the measurements of my mold. But how do I then adjust the recipe? I tripled the recipe and I had too much and had to scramble for something else to use as a mold.

By the way, I love your website and so happy I found it! I did the room temp method today and can't wait to unveil it tomorrow! I will never go back to the cold process again! My next adventure is to try the hot process. Thanks!


Once you have used the calculation for mold volume to determine how much oil your recipe will need, you simply put that number into section 2 of SoapCalc and then input the percentages of your oils in the recipe into sections 6 and 7. Fill in the remainder of the of the soap calculator and hit calculate.

For example:

Using this formula...

Length of mold x Width of mold x Height of soap x .40 = ounces of oil needed

My mold is 6" x 6" and I pour my soap to 2.25" high so the calculation will be:

6" x 6" x 2.25" x .40 = 32.4 ounces

The calculation is done if you measure in ounces. Since I like working in grams, I convert the ounces over by mulfiplying the ounces by 28.375

32.4 ounces x 28.375 = 919.35 grams

Now that I know I need 919.35 grams of oil in my recipe, I place that number in section 2 of SoapCalc and I select the "grams" button since that is what I prefer to weigh my ingredients out in.

If I want to use the basic recipe:

Coconut 30%
Palm 30%
Olive 40%

Superfat 8%
Water as a percent of oil 36.23%

I input those ingredients and percentages into sections 6 and 7.

I adjust the Water as a percent of oil in section 3 to 36.23% and the superfat in section 4 to 8%.

Then all I have to do is hit the "Calculate Recipe" button and the "View or Print Recipe" button.

That's it!

Good luck and have fun!


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metric version
by: Anonymous

The formula for metric is

lxwxh*0.6918 where measurements are in cm.

So a 1 litre mold takes 690g of oil

covert to cm?
by: Anonymous

is there a way to convert this hole thing to cm intead of inches because in need to convert firt the cm in to inches and then ad is in the formula.

and then calculate is back is there not a way to convert every thing so i dont need to convert the cm in to inches and then ad the formula.

What if it's an irregular mold?
by: Anonymous

How would you figure this out if you had an irregular shaped mold but you know (because of the manufacturer) that the mold holds, say 5lbs?

What size loaf do you use for this example?
by: Rose

what size is your 6x6x2.25 loaf? When you cut your soap do you do 4 oz-2.25" size bars?

What is the .40?
by: Anonymous

What does the .40 mean on your calculations for oils? Is that the percentage of oils you are putting in the soap or something different? Great site!


The mold calculation is not mine but one that has been posted for many years on one of the soap forums.

I believe the .40 takes out the approximate volume of water in your recipe leaving you with the amount of oil needed to put into a lye calculator.

Even though we most often use a bit less water, this makes sure that your soap mold will be big enough for your recipe.


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