Overview
How it's calculated
Enter your weight, height and body-fat percentage (use the body-fat calculator if you don't know it). We compute fat-free mass, divide by height squared, then normalize to a 1.8 m reference so people of different heights can be compared.
fat-free mass = weight × (1 − bodyfat%) FFMI = FFM / height(m)² normalized = FFMI + 6.1 × (1.8 − height_m)
How to read your result
For men, ~18–20 is average, 22–23 is excellent, and the mid-20s approach the natural ceiling; values much above ~25 are uncommon without exceptional genetics. Use it to track muscle gain, not as a hard limit.
Frequently asked questions
What's a good FFMI?
Around 18–20 is average for trained men, 22–23 is excellent, and ~25 is near the natural upper range. Women's reference values run lower.
Why normalize FFMI?
Normalizing to 1.8 m height removes the bias that taller people get higher raw scores, making comparisons fairer.
Do I need an accurate body-fat number?
Yes — FFMI is sensitive to body-fat input. Use a consistent method (e.g. the Navy estimate) so your trend is meaningful.
Sources & references
- Kouri EM, Pope HG, Katz DL, Oliva P. Fat-free mass index in users and nonusers of anabolic-androgenic steroids. Clin J Sport Med. 1995;5(4):223-228.
Medical disclaimer
This calculator is for general educational purposes only and is not medical advice. Estimates are based on population formulas and may not fit your individual situation. Consult a qualified healthcare or fitness professional before making health, nutrition or training decisions.