What the number means
A SAP value is usually given in milligrams of potassium hydroxide (KOH) per gram of oil. SoapCalc notes that potassium hydroxide is for liquid soap, while bar soap uses sodium hydroxide (NaOH), which is lighter per molecule, so divide the KOH figure by 1.403 (56.11 ÷ 40.00) to get the NaOH figure.
Every oil has its own range. These are the limits in the Codex Alimentarius food-oil standards:
| Oil | SAP (mg KOH per g) |
|---|---|
| Coconut | 248 to 265 |
| Palm kernel | 230 to 254 |
| Palm | 190 to 209 |
| Olive | 184 to 196 |
Higher values mean the oil needs more lye per gram.
How it’s used
This shows how a calculator works. Don’t use it as a recipe.
For 500 g of olive oil at a SAP value of 190: 500 × 190 ÷ 1000 = 95 g of KOH, or 95 ÷ 1.403 = 67.7 g of NaOH to react with all the oil. A 5% superfat takes off 5%, leaving about 64.3 g.
Across olive oil’s whole range (184 to 196), the same 500 g needs anywhere from 65.6 to 69.9 g of NaOH. SoapCalc notes that a SAP value is only an average unless your oil has been tested, which is one reason soap makers leave a superfat as a safety margin.
Lye safety
Sodium hydroxide causes eye and skin burns. NIOSH lists water, acids and metals such as aluminium, tin and zinc as things it reacts with. Use a soap calculator with the exact oils you have, wear eye and skin protection, and follow the lye supplier’s safety instructions.