Saponification Value Calculator

Work out saponification value instantly with clear inputs, formula shown and shareable results.

About Saponification Value Calculator

The saponification value is the alkali needed per gram of oil. Sodium hydroxide values are commonly quoted as grams per gram; potassium hydroxide requires 1.403 times as much because of its higher molar mass. Technical alkali is 90-99% pure, so the weighed quantity must be grossed up.

Formula

Alkali requirement

Pure alkali = oil mass x SAP value x (1.403 for KOH); actual = pure / purity

Worked example

With the default values below, Saponification Value Calculator returns Alkali Required of 195.876. Change any input above and every figure here is recalculated in your browser.

Inputs used

Oil Massminimum 0 g: 1,000 g
Saponification Valueminimum 0 g NaOH per g oil: 0.19 g NaOH per g oil
Alkalione of Sodium hydroxide (bar soap), Potassium hydroxide (liquid soap): Sodium hydroxide (bar soap)
Alkali Purityaccepts 0–100 %: 97 %

Results

Alkali Required: 195.876
Pure Alkali Needed: 190.000
Minimum Water For Lye Solution: 293.814
Saponification Value In mg KOH/g: 266.57

Step by step

1Values used
2Alkali requirement
3Alkali Required= 195.876
4Pure Alkali Needed= 190.000
5Minimum Water For Lye Solution= 293.814
6Saponification Value In mg KOH/g= 266.57

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
Sodium and potassium hydroxide are severely corrosive and generate heat when dissolved. Use eye protection, gloves and ventilation, and never add water to solid alkali.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Sodium and potassium hydroxide are severely corrosive and generate heat when dissolved. Use eye protection, gloves and ventilation, and never add water to solid alkali.

Frequently Asked Questions

Why does each oil have a different SAP value?

Because it depends on the average molecular weight of the fatty acids. Coconut oil with short chains needs more alkali per gram than olive oil with longer chains.

What if a blend of oils is used?

Calculate each oil separately and sum the alkali. Using an average SAP value across a blend introduces error, particularly with coconut or castor oil in the mix.