Iodine Value Calculator
The iodine value (IV) of a fat or oil measures its total degree of unsaturation as grams of iodine (I2) absorbed per 100 g of sample. Each carbon-carbon double bond (C=C) in the fatty acid chains reacts with one molecule of I2 (MW 253.81 g/mol). A pure triolein (olive-oil-type triglyceride with 3 oleic chains, each with 1 double bond, MW 885 g/mol) has a theoretical IV of (3 x 253.81 x 100) / 885 = 86.05. Enter the number of double bonds per molecule and the molecular weight of the fat to calculate the theoretical IV and the equivalent millimoles I2 per gram.
Iodine value formula
IV (g I2/100 g) = (n x 253.81 x 100) / MW
Where n is the number of C=C double bonds per molecule, 253.81 g/mol is the molar mass of molecular iodine (I2), and MW is the molar mass of the fat in g/mol. Each C=C consumes exactly one mole of I2 via electrophilic addition.
Iodine value classification of oils
- Non-drying oils (IV below 100): coconut, palm, olive; low unsaturation, stable, no film formation.
- Semi-drying oils (IV 100 to 130): corn, sunflower, sesame; partially polymerise on exposure to air.
- Drying oils (IV above 130): linseed, tung, oiticica; polymerise on air exposure to form a hard film, used in paints.
Iodine value: frequently asked questions
What is the iodine value of a fat or oil?
The iodine value (IV), also called the iodine number, is the grams of iodine (I2) absorbed by 100 g of fat or oil. It measures the degree of unsaturation: each double bond in the fatty acid chain reacts with one molecule of I2. Higher IV means more double bonds and greater unsaturation.
What is the iodine value formula?
IV = (n x 253.81 x 100) / MW, where n is the total number of C=C double bonds per molecule, 253.81 g/mol is the molar mass of I2, and MW is the molar mass of the fat in g/mol. The factor 100 scales to 100 g of fat.
What are typical iodine values for fats and oils?
Coconut oil: 7 to 12 g I2/100 g (highly saturated). Olive oil: 75 to 94 g I2/100 g (mainly oleic C18:1). Sunflower oil: 110 to 143 g I2/100 g (mostly linoleic C18:2). Linseed oil: 170 to 204 g I2/100 g (highly unsaturated, C18:3 dominant).
How is iodine value measured in the laboratory?
The Wijs method (ASTM D1959, AOCS Cd 1-25) dissolves the fat in an organic solvent, adds an excess of Wijs reagent (iodine monochloride in acetic acid), and back-titrates the excess with sodium thiosulfate. The iodine absorbed equals the iodine value.
What does a high iodine value mean for drying oils?
Oils with IV above 130 are called drying oils because the highly unsaturated fatty acids undergo oxidative polymerization when exposed to air, forming a hard film. Linseed oil (IV 170 to 204) and tung oil are classic drying oils used in paints and varnishes.
Official sources
- AOCS (American Oil Chemists Society): Official Method Cd 1-25 (Iodine Value, Wijs method).
- NIST Chemistry WebBook: Iodine molecular weight and fatty acid data.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.