Lye Calculator for Cold Process Soap

Calculate exact lye and water amounts for cold process soap recipes with multiple oil options and custom superfat percentages.

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About This Tool

This professional lye calculator helps soap makers create accurate cold process soap recipes. Enter oil amounts, select from common soap-making oils, set your desired superfat percentage, and optionally add fragrance. The calculator uses precise saponification values to determine the exact amount of sodium hydroxide (lye) and water needed for safe, properly saponified soap. All calculations are performed client-side for instant results without server delays.

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How to Use

Select oils from the dropdown menu or choose 'Custom Oil' to enter your own saponification value
Enter the amount of each oil in grams or ounces
Set your desired superfat percentage (typically 5-8%)
Optionally add fragrance oil percentage
Click 'Calculate Recipe' to get precise lye and water amounts
View the complete soap recipe with safety notes

Frequently Asked Questions

Find Quick Answers

What is superfat percentage in soap making?

Superfat percentage is the amount of excess oil left unsaponified in your soap. This makes the soap milder and more moisturizing. Typical superfat percentages range from 5-8% for cold process soap.

Why do I need to calculate lye precisely?

Accurate lye calculation is crucial for soap safety. Too much lye creates caustic soap that can burn skin, while too little results in soft, oily soap that doesn't last. This calculator ensures proper saponification.

Can I use this calculator for hot process soap?

Yes, the lye calculations are the same for both cold and hot process soap. The main difference is in the water amount and cooking process, but the lye-to-oil ratio remains identical.

What water-to-lye ratio should I use?

This calculator uses a standard 2:1 water-to-lye ratio (2 parts water to 1 part lye by weight), which is common for cold process soap. You can adjust this in the advanced settings if needed.

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