Sign inSign up
Interactive calculator

FFMI & Lean Body Mass
Calculator

Enter your weight, height and body-fat percentage to get your Fat-Free Mass Index, lean mass and fat mass — and see how your muscularity compares to natural-population norms.

  • Free · no sign-up
  • Runs in your browser
  • Nothing stored

Your numbers

Used only to interpret FFMI norms.
lbs
in
%
Don't know it? Estimate it with ourBody-Fat Calculator first.

Your FFMI

21.2

Normalized to 1.8 m: 21.3

Above average

Lean body mass66.9 kg · 147.6 lb
Fat mass14.7 kg · 32.4 lb
Lean mass share82%

Interpretation bands come from studies of natural lifters (male norms; female norms run roughly 3 points lower). The often-quoted "natural ceiling" near a normalized FFMI of 25 is a population heuristic — genetic outliers exceed it without enhancement — not a hard rule.

This calculator is for educational purposes only and is not medical advice, diagnosis, or treatment. Results are estimates based on published formulas and population averages — your individual values may differ. Nothing here is calculated on a server: everything runs in your browser and no data is stored or sent anywhere. Always consult a qualified clinician before making health, medication, or training decisions.