Work out soap making lye calculation instantly with clear inputs, formula shown and shareable results.
Lye is the oil weight times the weighted saponification value, reduced by the superfat percentage, with water added as a multiple of the lye weight. Superfat leaves a few percent of oils unsaponified for a milder bar, and getting the lye wrong in the other direction produces a caustic soap that must be discarded.
Lye quantity
lye = total oils x SAP value x (1 - superfat)
Water
water = lye x water to lye ratio
Sodium hydroxide is caustic. Always verify quantities against a dedicated soap calculator and the SAP values for your specific oils before mixing.
lye = total oils x SAP value x (1 - superfat). Lye is the oil weight times the weighted saponification value, reduced by the superfat percentage, with water added as a multiple of the lye weight.
Superfat leaves a few percent of oils unsaponified for a milder bar, and getting the lye wrong in the other direction produces a caustic soap that must be discarded.
Enter total oils, weighted sap value for sodium hydroxide, superfat (lye discount), water as a multiple of lye. The defaults shown are a realistic worked example — swap in your own figures to get a result you can use.