Your muscle mass, scored fairly.
Enter your weight, height and body fat percentage and see your Fat-Free Mass Index instantly, along with the height-normalized FFMI, your muscularity category, and how close you sit to the natural genetic ceiling.
Your measurements
Body weight in kilograms.
Height in centimeters.
Body fat percentage. Use a Body Fat Calculator or DEXA scan if unknown.
The formula is FFMI = fat-free mass (kg) / height (m)², where fat-free mass = weight x (1 - body fat % / 100). Results update as you type.
What your FFMI means
Where you sit on the FFMI scale
FFMI milestones at your height and body fat
FFMI categories for men and women
Thresholds are calibrated for men; women typically run about 2 points lower. The highlighted row is your current category (men's scale).
| Category | Men (FFMI) | Women (FFMI) |
|---|
FFMI, explained
Why FFMI Beats BMI for Athletes
BMI penalizes muscular bodies, a lean weightlifter often shows as overweight or obese. FFMI removes body fat from the equation and measures only the lean mass relative to height, giving a fair score for resistance-trained individuals. Bodybuilders, gymnasts, and Olympic weightlifters routinely score 24-26 FFMI while having essentially perfect body composition.
FFMI Categories (Men)
Below 18: Below average. 18-20: Average. 20-22: Above average, typical recreational lifter. 22-23: Excellent, dedicated natural athlete. 23-26: Superior, advanced natural athlete. 26-28: Suspicious, near the natural genetic limit. Above 28: Likely enhanced (drug use highly probable).
The Natural Limit Hypothesis
Research on drug-tested bodybuilders (Kouri et al. 1995) found that the upper limit for naturally trained men is roughly FFMI 25-26. Almost no documented drug-tested athletes exceed 26. Values above 28 are very rarely seen without performance-enhancing drugs. This makes FFMI useful for evaluating natural-physique claims.
Adjusted FFMI for Tall and Short People
Raw FFMI slightly favors shorter people because lean mass scales nonlinearly with height. The adjusted formula normalizes to a 1.8m height: Adjusted FFMI = FFMI + 6.1 × (1.8 - height_m). Use the adjusted value when comparing across heights. For a 1.8m person, raw and adjusted are equal.
Common questions
Is FFMI different for women?
Yes, women typically have a 2-3 point lower natural ceiling than men. The categories above are calibrated for men. For women, subtract roughly 2 points from each threshold.
What is the 'natural limit' claim?
Research on drug-tested bodybuilders suggests an FFMI ceiling around 25-26 for naturally trained men. Values above 28 are very rarely seen without performance-enhancing drugs.
How do I measure body fat accurately?
DEXA scan (most accurate, $50-150), hydrostatic weighing (very accurate), BodPod ($30-50), or 7-site skinfold caliper (good if done by trained person). Bioelectrical impedance scales are convenient but vary ±5%.
Is FFMI more useful than body fat percentage alone?
They measure different things. Body fat % tells you composition. FFMI tells you muscle mass relative to height. Both together give a complete picture of physique.
Can FFMI be too high?
Above 28 in men is essentially impossible without drugs. Above 26 is at the natural genetic ceiling. These extreme values can correlate with cardiovascular strain even if lean.
FFMI is an estimate that depends entirely on how accurate your body fat percentage is: cheap impedance scales can be off by 5 points, which shifts FFMI by a full point or more. It is a fitness benchmark, not a medical measurement. Do not use it to make health or training decisions on your own: talk to a doctor, coach or another qualified professional about what your result means for you.