Soap Lye Calculation: SAP Values, Superfat, and Safe Batch Records

Lye calculations must be oil-specific and independently checked.

Each fat or oil has a saponification value that estimates the alkali needed for conversion. Values vary by reference and material. A formula must use the correct NaOH or KOH basis and account for the actual purity of the alkali.

Build the calculation from reliable inputs

Superfat reduces the calculated lye amount but is not a substitute for accurate weighing, supplier records, protective equipment, ventilation, or a validated process. Changes to oil composition require a complete recalculation.

Turn the answer into a repeatable process

Keep the formula version, oil lots, SAP source, lye purity, water method, temperatures, actual weights, observations, and cure results with every batch. Independently verify unfamiliar formulas before production.

Try it with your own numbers

Use the free soap lye and superfat calculator as a transparent planning check, not as a replacement for training and safe handling.

This guide is educational and US-focused. Requirements and professional advice depend on your product, process, claims, sales channels, and location. Verify current official requirements before relying on a compliance decision.