Fat Free Mass Index Calculator
Two people can weigh the same but carry very different muscle. Enter your weight, height and body fat percentage, and this tool works out your lean mass, your Fat-Free Mass Index (FFMI) and the height-normalised FFMI for fair comparison.
Enter your details above and the result will appear here.
How to use
- Enter your weight and height.
- Enter your body fat percentage — use a recent measurement, not a guess.
- Your lean mass, FFMI and normalized FFMI appear instantly.
- Compare your normalized FFMI with the bands in the note below to see where you stand.
Note
FFMI = lean mass (kg) divided by height (m) squared. Normalized FFMI adds 6.1 x (1.8 - height in m) to adjust to a 1.8 m reference. General bands: below 18 low, 18 to 20 average, 20 to 22 above average, 22 to 25 very muscular, above 25 is rare without assistance — bands are community conventions, not medical categories. Estimate only — not medical advice.