Free body composition tool
FFMI Calculator
The fat-free mass index divides the mass of everything in your body except fat by your height squared. It is the lean-mass counterpart of BMI. Enter your weight, height and body fat.
Worked example
Someone who weighs 75 kg, is 178 cm tall and has 18% body fat has 61.5 kg of fat-free mass. That is an FFMI of 19.4 kg/m², and 19.5 kg/m² once adjusted to a height of 1.8 m.
Calculate your FFMI
The result below starts from the example's numbers. Change any field and it updates as you type.
Track this target every day
Use the number above as your daily goal in CalorTracker, then log meals by photo, voice or text and see where your day stands against it. Free to start, no card needed to explore.
Results are estimates from published formulas, not medical advice. Your own body can sit above or below them.
Where the formulas come from, and how we check them: how we calculate.
The formula
Fat-free mass is weight × (1 − body fat ÷ 100). The index divides it by height in metres, squared: FFMI = fat-free mass (kg) ÷ height² (m²). Taller people carry more fat-free mass, so Kouri and colleagues (1995) added a correction that restates every result for a man 1.8 m tall: normalized FFMI = FFMI + 6.3 × (1.8 − height in m). The calculator shows both.
Some sites print 6.1 instead of 6.3 in the correction. This calculator uses 6.3 because that is the figure in the abstract of the 1995 paper. The difference is small, under 0.1 for most heights.
Where the number comes from
Kouri and colleagues studied 157 male athletes, 83 of whom used anabolic-androgenic steroids and 74 of whom did not. They reported that normalized FFMI among the non-users reached an upper limit of 25.0, that many users were well above it and some above 30, and they called the findings preliminary. It was a study of men, with body fat measured one way, and it does not turn 25 into a target, a limit or a test for any individual. This page does not label any result.
The catch: it depends on the body fat you enter
FFMI is only as accurate as the body fat percentage behind it. A few percentage points of body fat move the result noticeably, and home estimates of body fat are rough. Use the same method each time if you want to follow your own change. If you are pregnant, have a medical condition, or are worried about your weight or your body, talk to your doctor. This page makes no health claims about any result.
Sources
Kouri EM, Pope HG, Katz DL, Oliva P, Clin J Sport Med 1995;5:223-228. All our sources are on the sources page.