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Lean body mass calculator
Short answer
Lean body mass is everything you weigh except fat: muscle, bone, organs and water. Three published equations estimate it from sex, height and weight. For a man of 180 cm and 80 kg they give 61.4 kg (Boer), 57.8 kg (Hume) and 61.7 kg (Janmahasatian). If you know your body fat percentage, lean mass is simply weight × (1 − body fat).
Last reviewed 27 October 20263 published sourcesNot medical advice
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Three published equations from height and weight, or an exact split if you know your body fat.
Enter your sex, height and weight to estimate your lean body mass.
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The three equations
With weight W in kg and height H in cm, Boer's equations are 0.407 W + 0.267 H − 19.2 for men and 0.252 W + 0.473 H − 48.3 for women (Boer, 1984).
Hume's are 0.32810 W + 0.33929 H − 29.5336 for men and 0.29569 W + 0.41813 H − 43.2933 for women (Hume, 1966).
Janmahasatian et al. modelled fat-free mass from DXA scans in 373 adults, including people with a BMI up to about 70: 9,270 × W ÷ (6,680 + 216 × BMI) for men and 9,270 × W ÷ (8,780 + 244 × BMI) for women (Janmahasatian et al., 2005).
| Person | Boer | Hume | Janmahasatian |
|---|---|---|---|
| Woman, 160 cm, 55 kg | 41.2 kg | 39.9 kg | 36.4 kg |
| Woman, 168 cm, 70 kg | 48.8 kg | 47.7 kg | 43.8 kg |
| Woman, 165 cm, 95 kg | 53.7 kg | 53.8 kg | 50.9 kg |
| Man, 175 cm, 70 kg | 56.0 kg | 52.8 kg | 55.9 kg |
| Man, 180 cm, 80 kg | 61.4 kg | 57.8 kg | 61.7 kg |
| Man, 180 cm, 115 kg | 75.7 kg | 69.3 kg | 74.3 kg |
Getting a better number
All three equations guess your body composition from your size. Any real body fat measurement beats them: get one from a scan or estimate it with the body fat calculator, then enter it above.
With a body fat figure you can also work out your FFMI, or set a protein target with the protein calculator.
Feed the muscle you have
Reps logs meals by photo, voice or text with a full macro breakdown, so your protein keeps pace with the lean mass you are building.
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Common questions
Which lean body mass formula is most accurate?
For people of average build the three agree within a few kilograms. Janmahasatian et al. built theirs because the older equations were inconsistent at extremes of size, and fitted it to DXA scans in a group that included very heavy people, so it is the better choice if you are well above or below average weight.
Is lean body mass the same as muscle mass?
No. Lean mass includes muscle but also bone, organs, skin and body water.
What is lean body mass used for?
Clinicians use it to dose some medicines, and coaches use it to set protein targets or to work out a fat-free mass index. Tracking it alongside body weight shows whether a change came from fat or from lean tissue.
Sources
Figures on this page were checked against these publications on 27 October 2026.
- Boer P. Estimated lean body mass as an index for normalization of body fluid volumes in humans. American Journal of Physiology. 1984;247(4 Pt 2):F632–F636. doi.org/10.1152/ajprenal.1984.247.4.F632
- Hume R. Prediction of lean body mass from height and weight. Journal of Clinical Pathology. 1966;19(4):389–391. doi.org/10.1136/jcp.19.4.389
- Janmahasatian S, Duffull SB, Ash S, Ward LC, Byrne NM, Green B. Quantification of lean bodyweight. Clinical Pharmacokinetics. 2005;44(10):1051–1065. doi.org/10.2165/00003088-200544100-00004
More body tools
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- Body fat calculatorBody fat percentage from a tape measure with the US Navy equations.
- FFMI calculatorFat-free mass index and the height-adjusted value, with the 25 limit in context.