The saponification value (SV or SAP value) is the number of milligrams of potassium hydroxide needed to saponify – turn into soap and glycerol – one gram of a fat or oil. Every triglyceride molecule consumes three hydroxide ions, so fats made of short fatty acids (more molecules per gram) have high values: coconut oil about 250–265, olive oil about 184–196.
In the lab the value is measured by back-titration. A weighed sample is refluxed with a known excess of alcoholic KOH, and the leftover KOH is titrated with standard hydrochloric acid. A blank without oil is run in parallel; the difference between the blank and the sample titres is the KOH used up by the fat. Food chemists use the value to check identity and detect adulteration, and soap makers use it to calculate the lye they need.
This calculator has three modes: the titration formula, a soap lye calculator (NaOH for bar soap, KOH for liquid soap) with superfat and purity, and a conversion from SV to the mean molar mass of the fat.
How to use the Saponification Value Calculator
- Mode
- HCl used for the blank (B)
- HCl used for the sample (S)
- Molarity of the HCl
- Mass of the oil or fat sample (W)
- Oil or fat
- SAP value (mg KOH/g)
- Mass of oil
- Lye
- Superfat (excess oil)
- Lye purity
- Lye concentration in the water
- Saponification value (mg KOH/g)
Results update as you type, every field has its own unit menu, and everything is calculated in your browser.
How it works
In titration mode the moles of KOH consumed are (B − S) × M of the acid; multiplying by 56.106 g/mol and dividing by the sample mass gives mg KOH per gram. For soap, the SAP value times the oil mass gives the KOH needed; for NaOH it is scaled by the ratio of molar masses (39.997/56.106) and reduced by the superfat, then divided by the lye purity.
Worked example
A 2.00 g sample of oil is refluxed with alcoholic KOH. The blank needs 24.5 mL of 0.5 M HCl and the sample 11.0 mL. KOH consumed = (24.5 − 11.0) × 0.5 = 6.75 mmol, or 6.75 × 56.106 = 378.7 mg, so SV = 378.7 ÷ 2.00 = 189.4 mg KOH/g – typical of olive oil. The average molar mass of the fat is about 3 × 56,106 ÷ 189.4 ≈ 889 g/mol, close to triolein (885 g/mol). For soap: 1000 g of olive oil (SAP 190) with 5% superfat needs 190 × 0.7129 × 0.95 = 128.7 g of NaOH, dissolved in 261.2 g of water for a 33% lye solution.
Saponification values of common oils and fats
Ranges from the Codex Alimentarius standards for named vegetable oils (CXS 210), olive oil (CXS 33) and animal fats (CXS 211); the lye mode uses the midpoint.
| Oil or fat | SV range (mg KOH/g) | Midpoint | NaOH (mg/g) |
|---|---|---|---|
| Coconut oil | 248–265 | 256.5 | 182.9 |
| Palm kernel oil | 230–254 | 242 | 172.5 |
| Palm oil | 190–209 | 199.5 | 142.2 |
| Olive oil | 184–196 | 190 | 135.4 |
| Soybean oil | 189–195 | 192 | 136.9 |
| Sunflower oil | 188–194 | 191 | 136.2 |
| Rapeseed oil, low erucic (canola) | 182–193 | 187.5 | 133.7 |
| Cottonseed oil | 189–198 | 193.5 | 137.9 |
| Groundnut (peanut) oil | 187–196 | 191.5 | 136.5 |
| Maize (corn) oil | 187–195 | 191 | 136.2 |
| Sesame oil | 186–195 | 190.5 | 135.8 |
| Safflower oil | 186–198 | 192 | 136.9 |
| Grapeseed oil | 188–194 | 191 | 136.2 |
| Lard | 192–203 | 197.5 | 140.8 |
| Beef tallow | 190–200 | 195 | 139.0 |
Inputs explained
| Field | What to enter |
|---|---|
| Mode | Choose one: Saponification value from a titration, Lye (NaOH/KOH) needed to make soap, Average molar mass from a SAP value |
| HCl used for the blank (B) | Units: mL, L, µL, cm³ (cc), fl oz (US) |
| HCl used for the sample (S) | Units: mL, L, µL, cm³ (cc), fl oz (US) |
| Molarity of the HCl | Units: mol/L (M), mmol/L (mM), µmol/L (µM), nmol/L (nM), mol/m³ |
| Mass of the oil or fat sample (W) | Units: g, mg, µg, kg, oz, lb |
| Oil or fat | Choose one: Coconut oil – SAP 256.5 mg KOH/g, Palm kernel oil – SAP 242 mg KOH/g, Palm oil – SAP 199.5 mg KOH/g, Olive oil – SAP 190 mg KOH/g … |
| SAP value (mg KOH/g) | A number |
| Mass of oil | Units: g, mg, µg, kg, oz, lb |
| Lye | Choose one: Sodium hydroxide, NaOH (bar soap), Potassium hydroxide, KOH (liquid soap) |
| Superfat (excess oil) | In % |
| Lye purity | In % |
| Lye concentration in the water | In % |
| Saponification value (mg KOH/g) | A number |
What each result means
- Water to dissolve the lye = [Lye to weigh out]×(100÷[Lye concentration in the water] – 1)
- Total batch (oil + lye + water) = [Mass of oil] + [Lye to weigh out] + [Water to dissolve the lye]
- Equivalent NaOH value = [Saponification value]×39.997÷56.106
- Average molar mass of the triglyceride = 3×56106÷[Saponification value]
Formula
SV (mg KOH/g) = (B − S) × M(HCl) × 56.106 ÷ W
B, S = mL of HCl for blank and sample; W = sample mass in g
NaOH for soap = oil mass × SV ÷ 1000 × (39.997 ÷ 56.106) × (1 − superfat)
Average molar mass of triglyceride ≈ 3 × 56,106 ÷ SV
Worked example
Inputs — Mode: Saponification value from a titration; HCl used for the blank (B): 24.5 mL; HCl used for the sample (S): 11 mL; Molarity of the HCl: 0.5 mol/L (M); Mass of the oil or fat sample (W): 2 g.
Results — Saponification value = 189.36 mg KOH/g; Equivalent NaOH value = 134.99 mg NaOH/g; Average molar mass of the triglyceride = 888.9 g/mol; KOH consumed = 6.75 mmol.
Key terms
- Saponification
- Alkaline hydrolysis of fats into glycerol and fatty acid salts (soap).
- SAP value
- Saponification value, mg KOH per gram of fat.
- Blank
- Titration run without the sample to measure the total KOH added.
- Superfat
- Percentage of oil deliberately left unsaponified in soap.
- Triglyceride
- Ester of glycerol with three fatty acids; the main component of fats and oils.
Frequently asked questions
What is a saponification value?
The mass of KOH in milligrams that saponifies 1 g of fat or oil. It is inversely related to the average chain length of the fatty acids.
How is it measured?
By refluxing about 2 g of oil with 25 mL of 0.5 M alcoholic KOH, then back-titrating the excess KOH with 0.5 M HCl against a blank (AOCS Cd 3-25 and ISO 3657 describe the method).
Why is coconut oil's SAP value so high?
It is rich in lauric (C12) and myristic (C14) acids, so a gram contains more triglyceride molecules than long-chain oils like olive oil.
How do I convert a KOH SAP value to NaOH?
Multiply by 39.997 ÷ 56.106 = 0.7129. An SV of 190 is 135.4 mg NaOH per gram.
What superfat should I use for soap?
5% is common for bar soap, leaving some unreacted oil for mildness and a safety margin against measurement errors.
Why does the purity of KOH matter?
Commercial KOH flakes are usually about 90% pure, so you must weigh more – divide by 0.90 – to deliver the right amount.
What does a low SV indicate?
Longer fatty acid chains or unsaponifiable matter such as waxes or mineral oil, which can reveal adulteration.