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.
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.
Frequently Asked Questions (FAQ)
What is the FFMI calculator for?
It calculates your fat-free mass index and normalized FFMI from weight, height and body fat percentage to gauge muscularity relative to height.
What inputs do I need?
Your weight in kilograms, height in centimetres and body fat percentage.
What do the results mean?
General bands: below 18 low, 18-20 average, 20-22 above average, 22-25 very muscular, above 25 is rare without assistance. These are community conventions, not medical categories.
What if I do not know my body fat percentage?
Use a recent measurement instead of a guess, from a smart scale, calipers, or a gym test. Retest the same way each time to track your trend.