Soap Making Calculator
Calculate lye and water amounts for cold process soap making.
Enter oil weight, lye concentration, and superfat percentage.
Soap Recipe
Cold process soap is made by combining oils with a lye (sodium hydroxide) solution.
Lye Amount = Oil Weight × SAP Value × (1 – Superfat%)
Water Amount = Lye Amount / Lye Concentration
SAP values (sodium hydroxide) vary by oil. A blended average of 0.135 is used here for a typical olive/coconut/palm blend.
Lye concentration is the ratio of lye to total solution:
- 25%: More water, slower trace, easier to work with
- 30%: Standard concentration, good balance
- 33%: Less water, faster trace, quicker unmolding
Superfat is extra oil that remains unsaponified:
- 3–5%: Standard, gentle on skin
- 5–8%: Extra moisturizing
- 8–10%: Very rich, shorter shelf life
Safety: Always add lye to water, never water to lye. Wear protective gear.