Soap Making Lye Calculator
NaOH (Bar Soap)
Calculate sodium hydroxide needed for cold process bar soap
KOH (Liquid Soap)
Calculate potassium hydroxide needed for liquid soap
Formula
Lye (oz) = Oil Weight (oz) × SAP Value × (1 - Superfat%/100)
Frequently Asked Questions
What is saponification?
Saponification is the chemical reaction between fats/oils and a strong base (lye) that produces soap and glycerin. Each oil has a unique SAP value indicating how much lye is needed to fully convert it.
What does superfat mean?
Superfat is the percentage of oils left unsaponified in the finished soap. A 5% superfat means 5% of the oils won't react with lye, resulting in a more moisturizing bar. Most soap makers use 3-8% superfat.
Why is safety important with lye?
Sodium hydroxide (NaOH) and potassium hydroxide (KOH) are caustic substances that can cause severe burns. Always wear gloves, goggles, and long sleeves. Work in a ventilated area and always add lye to water.
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