Soap lye calculator
SAP values used
Grams of sodium hydroxide needed to saponify one gram of oil. For potassium hydroxide, multiply by 1.403.
| Oil | NaOH SAP |
|---|
Questions
What is superfat?
The percentage of oils left unsaponified, which makes soap gentler and guards against small measuring errors. 5% is common for bar soap.
What's the difference between NaOH and KOH?
Sodium hydroxide (NaOH) makes solid bar soap. Potassium hydroxide (KOH) makes soft or liquid soap. They aren't interchangeable gram for gram.
How much water should I use?
A common starting point is water equal to 38% of the oil weight, or a lye concentration of about 30–35%. Less water speeds up trace and shortens cure time.
Can I trust these numbers?
SAP values vary slightly between batches of oil. The values here are standard averages; always double-check a new recipe with a second calculator or your supplier's data.