FFMI Calculator
Your Fat-Free Mass Index — how much muscle you actually carry for your height. Like BMI, but it doesn't punish you for being jacked.
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What FFMI actually tells you
What is FFMI?
FFMI (Fat-Free Mass Index) measures your lean, fat-free mass relative to your height — like BMI, but for muscle instead of total weight. It's fat-free mass in kilograms divided by height in metres squared.
What is a good FFMI?
For men, ~18–20 is average, 20–22 is well-trained, and 22–25 is advanced/excellent. A normalized FFMI around 25 sits near the natural (drug-free) ceiling. Women typically run about 2–3 points lower.
What is the natural FFMI limit?
A well-known 1995 study (Kouri et al.) found drug-free lifters rarely exceed a normalized FFMI of about 25, while steroid users regularly went above it. ~25 is the widely-used natural upper limit — genetics move it a point either way.
How is FFMI calculated?
FFMI = fat-free mass (kg) ÷ height (m)². Fat-free mass = weight × (1 − body-fat%). Normalized FFMI adds 6.1 × (1.8 − height in m) so tall and short lifters compare fairly.
FFMI vs BMI — what's the difference?
BMI counts all your weight, fat included, so muscular people get mislabeled "overweight". FFMI isolates lean mass, so it reflects how much muscle you actually carry — a far better number for athletes.