Medical & Clinical
FFMI Calculator
BMI punishes muscle. FFMI is the metric that finally credits it — the honest number for people who lift.
Fat-free mass index (FFMI) normalizes lean body mass by height: lean kg ÷ height in metres squared. For men, 18–20 is average, 22–23 excellent, and sustained values above 25 are rare without extraordinary genetics or pharmacology. Interpretation belongs to your clinician — use these numbers to ask better questions.
FFMI = lean mass ÷ height².
Men: 22–23 = excellent.
Above 25 = rare naturally.
Calculate Your Fat-Free Mass Index
Your FFMI
What Is Fat-Free Mass Index?
FFMI is BMI's fairer sibling: instead of total weight, it indexes lean mass — muscle, bone, and organs — against height squared. That makes it the go-to metric for athletes whose BMI reads 'overweight'.
Population studies of trained men give the reference ladder: 18–20 average, 22–23 excellent, 25+ the territory of elite bodybuilders — which is why values far above 25 raise questions about pharmacological assistance.
How It Is Calculated
FFMI = lean mass (kg) ÷ height² (m²)
Lean mass = weight × (1 − body fat % ÷ 100)
Example: Example: 82 kg at 14% body fat, 178 cm → lean 70.5 kg → FFMI 22.3 (excellent)
FFMI reference (trained men)
| FFMI | Rating |
|---|---|
| < 17 | Below average |
| 17–19 | Average |
| 19–21 | Above average |
| 21–23 | Excellent |
| 23–25 | Superior |
| ≥ 25 | Elite — rare naturally |
Limitations
- Reference bands derive from male populations; female norms sit a few points lower.
- Accuracy depends on an honest body-fat input.
- The 'natural limit' discussion is statistical, not diagnostic.
Sources & Review
References used for this calculator’s formulas and thresholds:
Fat-Free Mass Index FAQ
What is a good FFMI?
21–23 reflects an excellent muscular build for trained men; 18–20 is the population average.
Is FFMI better than BMI for lifters?
Yes — FFMI indexes lean mass only, so muscle is credited instead of penalized.
What is the natural FFMI limit?
Statistically, sustained values above ~25 are extremely rare without pharmacology — the basis of the 'FFMI limit' discussion.
Important disclaimer: Results are educational estimates, not a substitute for professional medical advice. Discuss your results with a qualified professional before making decisions.