Body composition calculator
FFMI calculator
Fat-Free Mass Index is BMI's muscle-aware cousin. Enter your weight, height, and body-fat percentage to see how much muscle you carry. Free, instant, no sign-up.
Track this number — the trend says more than today's reading.
Free — no card, 30 seconds. Your result comes with you.
What is FFMI?
Fat-Free Mass Index is BMI's muscle-aware cousin. Instead of dividing total weight by height squared, it divides your lean mass, so it tracks how much muscle you carry for your frame.
How this calculator works
First we calculate fat-free mass: weight × (1 − body-fat%). Then FFMI = fat-free mass ÷ height in metres squared. The normalized version adds 6.1 × (1.8 − height in metres), so taller and shorter lifters can be compared on the same scale.
FFMI chart for men and women
The same FFMI formula works for men and women; the interpretation changes because average lean mass differs. Treat any FFMI chart as a broad reference, not a verdict. The useful comparison is usually your own normalized FFMI over time, measured with the same body-fat method.
Reading your number
Roughly, 18–20 is average, 20–23 is clearly athletic, and the drug-free ceiling sits around 24–25. The result depends on an accurate body-fat figure, so treat it as a ballpark. The coach can build training and nutrition to add lean mass over time.