Mold Calculator
Pick your Nurture mold or enter your own mold's size to see how much oil fills it. Then take that number straight into the Lye Calculator.
Shop soap moldsWhat it's for
Tells you how much oil fills your mold, so you don't end up with too much or too little soap.
You'll need
The name of your Nurture mold, or your own mold's inside length and width and how high you'll fill it.
Example loaded: the 2 lb Basic Soap Mold. Scroll down to see how much oil fills it, then press Use this in the Lye Calculator to make your recipe.
Example loaded: a homemade loaf mold, 9 by 3.5 inches inside, filled 3 inches high. Scroll down to see how much oil fills it.
Leave blank to fill to the top.
Measure the inside of the mold. For a round cavity, enter the diameter as both length and width.
Oils to use
Next steps
Use this in the Lye Calculator Get your lye and water for this much oil. Work out the fragrance How much fragrance oil for this batch? Work out the cost What will each bar cost you?This is the weight of oils (and butters) only. The Lye Calculator adds the lye and water. Liners flex a little, so treat it as a close starting point and leave a little room at the top if you want to texture.
Good to know
How is this worked out?
We use 0.40 oz of oils for every cubic inch of mold (about 0.69 g per cubic centimeter). It's the same rule behind the capacities on our mold pages. Once lye and water are added, that much oil fills the mold to the height you entered.
This is based on a 30% lye concentration (the Soap Calculator's default, about 33% water as a percent of oils). With full water, your batter will sit a little higher, about 3 to 4% more. With a bigger water discount, it will sit a little lower.
Should I pick the liner or the wood box?
Our mold sets list two capacities. The silicone liner is the size most people use. If you line the wood box with freezer paper instead, it holds a little more, so pick that option to see the bigger batch.
Can I make a shorter loaf?
Enter a fill height to see the oils for a shorter loaf, for example 2" instead of 2.5". The bar count stays the same; the bars are just shorter.
See a problem or have an idea? Help us make this better.
These tools are new, and we're still fine-tuning them. If something looks off, like a number that doesn't add up, a missing product or a confusing step, email us at our contact page and we'll fix it. Have an idea, or a tool you'd like us to make? We'd love to hear that too!
These tools are new. Tell us what's off, or what you'd like us to make:
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© 2026 Nurture Handmade. This tool, its data and its wording are ours. Please don't copy, scrape or republish them. See our Terms of Service.