Fat-Free Mass Index Calculator
This calculator estimates your Fat-Free Mass Index (FFMI), a measure of muscle mass relative to height, often used in fitness and bodybuilding. It calculates lean body mass and adjusts FFMI based on a standardized height of 1.8 m (5 ft 11 in) to compare physiques across individuals.
FFMI and Adjusted FFMI Calculator
Fat-Free Mass Index Formulas
$$\text{Lean Mass} = \text{Weight} \times \left( 1 – \frac{\text{BodyFat}}{100} \right)$$
$$\text{FFMI} = \frac{ \left( \frac{\text{Lean}}{2.2} \right) }{ \left( \left( \text{Height (ft)} \times 12 + \text{Inches} \right) \times 0.0254 \right)^2 }$$
$$\text{Adjusted FFMI} = \text{FFMI} + \left( 6 \times \left( \left( \left( \text{Height (ft)} \times 12 + \text{Inches} \right) \times 0.0254 \right) – 1.8 \right) \right)$$
The Fat-Free Mass Index (FFMI) provides a height-normalized value of lean body mass, useful for assessing muscular development.
- Lean body mass is computed from total weight and body fat percentage.
- FFMI is often used to benchmark natural muscular limits in athletes.
- Adjusted FFMI removes height bias, allowing fairer comparisons.
FFMI Interpretation (Men):
- < 18: Below average
- 18–20: Average
- 20–22: Above average
- 22–25: Excellent
- > 25: May indicate steroid use
FFMI Interpretation (Women):
(Generally 2–3 points lower than male values)
It’s commonly used with food tracking apps and nutritional plans.