What is normalized FFMI?
It adjusts FFMI toward a 1.8 m reference height so taller and shorter people compare more fairly.
FFMI Calculator
FFMI puts muscle mass in context by adjusting fat-free weight for height—useful for tracking lean gains.
Weight, height, body fat
Enter height, weight, and your estimated body fat percentage.
About this calculator
How to use FFMI Calculator, plus the formulas and logic behind the results.
Tool description
Fat-free mass index (FFMI) expresses lean mass relative to height squared, similar to BMI but for muscle. Normalized FFMI adjusts for height above or below 1.8 m.
How to use
- Choose units and enter height and weight.
- Add a body fat % estimate from calipers, scale, or prior testing.
- Calculate to see FFMI and normalized FFMI.
- Track over time rather than comparing to extreme outliers.
Formulas & reference
Fat-free mass = weight × (1 − BF%÷100)FFMI = fat-free mass ÷ height(m)²Normalized FFMI = FFMI + 6.1 × (1.8 − height(m))
Rough FFMI context (men)
- Average: ~18–20
- Muscular trainee: ~22–25
- Advanced natural lifter: ~25–26
- Values above ~26 are uncommon without exceptional genetics or pharmacology
Calculation logic
Body fat percentage removes fat mass from total weight. FFMI divides fat-free mass by height in meters squared, then height normalization is applied.
Body fat input quality drives accuracy. FFMI is informative for lifters but not a medical diagnostic.
FFMI Calculator FAQ
Common questions about this calculator and how to use the results.
Do I need DEXA for body fat?
Any reasonable BF% estimate works, but better input yields better FFMI.
Is high FFMI always healthy?
Not necessarily—it reflects lean mass, not cardiovascular fitness or joint health.
Can women use this?
Yes. Interpretation differs; women typically have lower FFMI at similar training levels.
Why include body fat?
FFMI needs fat-free mass, which requires knowing or estimating fat mass.
How often to recheck?
Every 8–12 weeks aligns with typical physique changes.