FFMI Calculator (2026)

FFMI (Fat-Free Mass Index) measures how much lean (non-fat) mass you carry relative to your height, similar to how BMI measures total weight for height. It is calculated as fat-free mass in kilograms divided by height in metres squared. Unlike BMI, FFMI is not skewed by body fat, so it is a better gauge of muscularity.

Normalised FFMI adjusts the raw value to a 1.8 m reference height using FFMI + 6.1 × (1.8 − height in m). This stops taller people from appearing artificially lower and shorter people higher, making comparisons fairer.

Research often cited from Kouri et al. found that drug-free male athletes rarely exceed a normalised FFMI of about 25. Values around 22–25 represent excellent, hard-earned natural muscularity; values well above 26 are uncommon without performance-enhancing drugs. These thresholds are best validated for adult men.

Yes — FFMI is based on lean mass, which requires body fat to separate from total weight. If you don't know it, estimate it first with our body-fat calculator. More accurate methods (DEXA, calipers) give a better FFMI; a rough body-fat guess gives a rough FFMI.