Body composition calculator
FFMI calculator
Fat-free mass index is a BMI-like number that accounts for muscle. Enter your weight, height and body fat to see where you sit.
What is FFMI?
Fat-free mass index relates your lean mass to your height the same way BMI relates total weight to height. Because it strips out fat, it is the number lifters use to compare muscularity across heights.
How it is calculated
Fat-free mass is weight × (1 − body fat). FFMI is that divided by height in metres squared. The normalised value adds 6.1 × (1.8 − height in m) so people of different heights can be compared on one scale.
Reading the number
Roughly 18–20 is average, 20–23 is clearly athletic, and 24–25 is near the drug-free ceiling. It depends on the accuracy of your body-fat measurement, so treat it as an estimate and track the change rather than the absolute.
FAQ
What is a good FFMI?
Around 18–20 is typical for untrained men, 20–23 shows serious training, and 25 is the commonly cited natural ceiling. Women run roughly 3–4 points lower.
Why normalise for height?
Taller people carry lean mass on a longer frame, which slightly deflates FFMI. Adding 6.1 × (1.8 − height in m) puts everyone on a 1.8 m reference.