Estimate fat-free mass from height and weight with three published equations side by side, or enter a known body-fat percentage for the more accurate direct method.
| Input | Result |
|---|---|
| Male, 80 kg, 180 cm | Boer 61.4 kg · James 62.7 kg · Hume 57.8 kg · avg 60.6 kg (75.8% of body weight) |
| Female, 65 kg, 165 cm | Boer 46.1 kg · James 46.6 kg · Hume 44.9 kg · avg 45.9 kg (70.6% of body weight) |
| Male, 180 lb, 71 in | Boer 137.1 lb · James 140.2 lb · Hume 128.8 lb · avg 135.4 lb (75.2% of body weight) |
| Female, 65 kg, 165 cm, body fat 24% | Measured 49.4 kg · Boer 46.1 kg · James 46.6 kg · Hume 44.9 kg · avg 45.9 kg (70.6% of body weight) |
Because these are three different regression equations fitted to three different populations, and they genuinely disagree, often by a couple of kilos. Boer (1984) was fitted for drug dosing and is the one most often used clinically today; James (1976) came from a large body-size survey; Hume (1966) is the oldest and was derived from cadaver and creatinine-clearance data. Showing all three tells you how much the answer depends on which equation you pick.
For healthy adults, Boer is the most widely cited in clinical work. If you have a DEXA scan or another measured body-fat figure, that number beats all three, put it in the body-fat field and the direct method takes over as the primary result.
No, deliberately. The Peters (2011) equation was built for children, but sources disagree on the age range it covers, we have seen both “up to 14” and “5 to 18”. Rather than publish a number we cannot pin down, we leave it out and say so. The three equations here are adult equations.
Nearly, but not quite. Fat-free mass excludes every lipid; lean body mass still includes the small amount of essential fat in cell membranes and nervous tissue. For most people the two differ by one or two kilos.
No. These are published population-level estimates, not a clinical measurement. Speak to a clinician before making dosing, dietary or medical decisions based on the result.