What is soap making lye calculator?
A soap lye calculator estimates the sodium hydroxide and water needed to saponify oils. This simplified version is for planning single-primary-oil recipes and must be checked against a trusted, full lye calculator before making soap.
How to use this calculator
- Choose the primary oil.
- Enter oil weight.
- Set superfat and water ratio.
- Verify the recipe with an established lye calculator and safety procedure before mixing.
How is it calculated?
Formula
lye = oil weight x SAP value x (1 - superfat); water = lye x water ratio What The Constants Mean
- Olive oil SAP value (0.134): Approximate NaOH SAP value for olive oil; verify with a full lye calculator.
- Percent divisor (100): Converts a user-entered percent into a decimal multiplier.
A 32 oz olive-oil recipe at 5% superfat uses about 4.07 oz sodium hydroxide and 8.15 oz water at a 2:1 water ratio.
Common mistakes
Soap making is chemistry. SAP values vary by source and oil composition, and lye errors can produce unsafe soap or dangerous handling conditions. Always measure by weight and use appropriate safety gear.
FAQ
Is this enough to make soap safely?
No. Use this as an estimate, then verify with a trusted full lye calculator and follow established safety procedures.
What is superfat?
Superfat is the extra oil left unsaponified by reducing the calculated lye amount.
Can I measure lye by volume?
No. Lye and oils should be measured accurately by weight.
What PPE do I need?
At minimum, follow soap safety guidance for eye protection, gloves, ventilation, and lye-safe containers.