Lean Body Mass Calculator
With weight 82 kg, height 178 cm, lean body mass comes to 61.7 kg — lean body mass (boer). It is reached in 7 steps, the last of which is 0.407 * 82 + 0.267 * 178 - 19.2, and each one is printed on the page with its numbers filled in. The formula is the one published by Boer P., not an approximation fitted to it.
Lean mass by the Boer, James and Hume equations side by side, with the fat mass each implies — the three disagree by kilograms, so the formula is the answer.
Formula and sources checked · How we check
Weight 82 kg, Height 178 cm, Sex Male
61.7 kg
Lean body mass (Boer) for the example below. Editing a field recomputes the calculator below; this figure holds the answer the page was loaded with.
It is written into the HTML rather than drawn by a script, so a search engine reading this page without running JavaScript still finds an answer.
- Boer
0.407 * 82 + 0.267 * 178 - 19.261.7 kg- James
1.1 * 82 - 128 * pow(82 / 178, 2)63.036 kg- Hume
0.3281 * 82 + 0.33929 * 178 - 29.533657.764 kg- Spread between the three
max(61.7, max(63.035753, 57.76422)) - min(61.7, min(63.035753, 57.76422))5.272 kg- Fat mass implied by Boer
82 - 61.720.3 kg- Body fat implied by Boer
20.3 / 82 * 10024.756 %- Lean mass index, LBM ÷ height²
61.7 / pow(178 / 100, 2)19.474
Worked example
An 82 kg man of 178 cm gets 61.7 kg by Boer, 63.0 by James and 57.8 by Hume — a spread of 5.3 kg, which is 6% of body weight and more than most people’s idea of their own margin of error. Boer implies 20.3 kg of fat, or 24.8%.
How to work it out yourself
- 1.Pick the formula for the purpose. Boer is what clinical pharmacy uses to normalise drug doses; James is the older equation still embedded in some anaesthetic references; Hume came from a 1966 autopsy series and reads low against the other two.
- 2.Treat any of them as an estimate from height and weight alone. None measures anything: they are regressions on cohorts, so an unusually muscular or unusually light-framed person sits outside the fit by definition.
- 3.Do not use James at high body weight. Its quadratic term turns the curve over, so above roughly 120 kg it starts returning smaller lean mass for larger people, which is an artefact of the fit rather than physiology.
Lean mass by weight, at this height and sex
| Weight (kg) | Lean body mass (Boer) | Boer | James | Hume |
|---|---|---|---|---|
| 60 | 52.7 kg | 52.75 kg | 51.46 kg | 50.55 kg |
| 70 | 56.8 kg | 56.82 kg | 57.2 kg | 53.83 kg |
| 80 | 60.9 kg | 60.89 kg | 62.14 kg | 57.11 kg |
| 90 | 65.0 kg | 64.96 kg | 66.28 kg | 60.39 kg |
| 100 | 69.0 kg | 69.03 kg | 69.6 kg | 63.67 kg |
| 120 | 77.2 kg | 77.17 kg | 73.83 kg | 70.23 kg |
The formula
- Boer
0.407 * 82 + 0.267 * 178 - 19.2 - James
1.1 * 82 - 128 * pow(82 / 178, 2) - Hume
0.3281 * 82 + 0.33929 * 178 - 29.5336 - Spread between the three
max(61.7, max(63.035753, 57.76422)) - min(61.7, min(63.035753, 57.76422)) - Fat mass implied by Boer
82 - 61.7 - Body fat implied by Boer
20.3 / 82 * 100 - Lean mass index, LBM ÷ height²
61.7 / pow(178 / 100, 2)
Source: Boer P. — Estimated lean body mass as an index for normalization of body fluid volumes (Am J Physiol, 1984), James W. — Research on obesity: a report of the DHSS/MRC group (1976), the equation clinical dosing inherited, Hume R. — Prediction of lean body mass from height and weight (J Clin Pathol, 1966)
Questions people actually ask
- What is lean body mass?
- Everything that is not fat: muscle, bone, organs, skin and body water. It is the complement of fat mass, so lean mass plus fat mass is body weight, and it is the quantity drug doses are normalised against because fat is poorly perfused.
- Which lean body mass formula is best?
- Boer, for most purposes — it is the one clinical pharmacy standardised on and it behaves sensibly across the normal weight range. James turns over at high body weight and Hume reads a few kilograms low. On the example above the three differ by 5.3 kg, so quoting a figure without naming the equation is quoting a number without units.
- Is lean body mass the same as fat-free mass?
- Nearly, and the distinction is pedantic in practice. Fat-free mass excludes all lipid; lean body mass as originally defined includes the small amount of essential lipid in cell membranes and the nervous system — about 2-3% of body weight. Every formula here is fitted to predict the same thing regardless of which name the paper used.
- How accurate is this?
- It is a regression on height, weight and sex, so it cannot see body composition at all. Against DXA the standard error of these equations is a few kilograms, and it is largest exactly where people care most — the very lean and the very heavy. For tracking a change over months, use the same formula each time and watch the direction rather than the absolute.
Related
- BMI CalculatorBody mass index from height and weight in either metric or US units, with the CDC category cut-offs.
- Body Fat CalculatorBody fat percentage from tape measurements using the US Navy circumference method, plus lean mass.
- BMR CalculatorBasal metabolic rate from the Mifflin-St Jeor, revised Harris-Benedict and Katch-McArdle equations at once, with the disagreement between them shown.
- Ideal Weight CalculatorReference weight from height by four standard clinical formulas, and the BMI-healthy range they sit inside.
- FFMI CalculatorFat-free mass index from weight, height and body fat, with the height-normalised version and the threshold the original study drew.
- Army Body Fat CalculatorThe Army’s waist-to-height assessment that replaced the tape test in July 2026, with the waist measurement the 0.55 standard allows at your height.
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