FFMI Calculator
How much muscle you carry for your height — the lean version of BMI.
Normalized FFMI
21
Above average- Raw FFMI21
Fat-Free Mass Index (FFMI) is like BMI but for lean mass only. It tells you how much muscle you carry relative to height, and is popular for gauging muscular development and natural-physique potential.
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.