BMI cannot tell muscle from fat. FFMI can.
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Fat-free mass index is like BMI but uses only your fat-free mass: FFMI = fat-free mass (kg) ÷ height (m)². The height-adjusted version adds 6.1 × (1.8 − height in metres).
For men, an adjusted FFMI of about 18–20 is average, 22–23 excellent, and around 25 is considered near the natural limit in research on drug-free athletes.
| Sex | Male |
| Units | Metric (kg, cm) |
| Weight | 85 |
| Height | 180 |
| Body fat | 15% |
| FFMI | 22.3 |
| Height-adjusted FFMI | 22.3 |
| Rating | Excellent |
| Fat-free mass | 72.3 kg |
| BMI for comparison | 26.2 |
FFMI 22.3.
| Sex | Female |
| Units | Metric (kg, cm) |
| Weight | 62 |
| Height | 168 |
| Body fat | 22% |
| FFMI | 17.1 |
| Height-adjusted FFMI | 17.9 |
| Rating | Above average |
| Fat-free mass | 48.4 kg |
| BMI for comparison | 22 |
FFMI 17.1.
For men around 20–22; for women about 16–18. Above 25 (men) is rare without drugs.
For muscular people, yes, because it ignores fat mass.
Only as accurate as your body fat estimate.
A 1995 study found drug-free men rarely exceeded about 25.