Measure muscularity relative to height. Enter your stats and body fat to get raw and normalized FFMI plus an interpretation.
The Fat-Free Mass Index (FFMI) measures how much lean mass you carry relative to your height — essentially a BMI that ignores body fat. It's popular among lifters because it puts muscularity on a single scale you can track over years, and because it hints at how much natural muscle a frame can hold. You need your weight, height, and an estimate of body fat percentage.
Raw FFMI is fat-free mass in kilograms divided by height in metres squared. Because taller people tend to score slightly lower on the raw number, the normalized FFMI adds a small height correction (6.1 × (1.8 − height in metres)) so people of different heights can be compared fairly. The normalized figure is the one most charts refer to.
Tip: FFMI is only as accurate as your body-fat input. Estimate it first with the body fat calculator or a lean body mass estimate for a more reliable score.
A frequently cited study found that drug-free athletes rarely exceed a normalized FFMI around 25, while values well above that were far more common among enhanced athletes. It's a guideline, not a hard ceiling — genetics, measurement error, and body-fat estimation all shift the number — but it's a useful reality check on what's typically achievable naturally.