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.
A note before you begin: this tool offers educational estimates only. It cannot replace advice from your doctor or another qualified professional.