Calculate lean body mass with three published formulas — Boer, James and Hume — shown together so the spread between methods stays visible. Runs entirely in your browser — your numbers never leave this device.
| Formula | Lean body mass (kg) | Implied body fat % |
|---|---|---|
| Boer | 61.42 | 23.2% |
| James | 62.72 | 21.6% |
| Hume | 57.79 | 27.8% |
Informational only. This calculator applies a published formula to the numbers you enter — it is not medical advice, a diagnosis, or a substitute for a clinician. Talk to a qualified professional about decisions concerning your health.
| Formula | Men | Women |
|---|---|---|
| Boer | 0.407W + 0.267H − 19.2 | 0.252W + 0.473H − 48.3 |
| James | 1.1W − 128(W÷H)^2 | 1.07W − 148(W÷H)^2 |
| Hume | 0.32810W + 0.33929H − 29.5336 | 0.29569W + 0.41813H − 43.2933 |
Lean body mass is body weight minus fat mass. Three regression formulas estimate it from weight and height alone, and this page calculates all three because they do not agree exactly: Boer is a linear equation in weight and height, James includes a squared weight-to-height term, and Hume uses a different linear fit from a different study population. Showing the three together makes the method spread part of the result rather than hiding it behind a single selected formula.
The worked examples quantify that spread. For the man in the first example the three formulas span 57.8 to 62.7 kg — a range of nearly five kilograms from the same two inputs. That spread is the accurate statement of what height-and-weight formulas can determine; a composition measurement by imaging or other laboratory methods is a different procedure with its own result.
Each formula's constants are printed in the table, by sex, exactly as published, so every figure on the page can be reproduced by hand. The output is informational arithmetic only.
Because the published formulas disagree by several kilograms on identical inputs — 57.8 to 62.7 kg in the first worked example. Presenting one figure alone would overstate the precision of a height-and-weight estimate.
Body weight minus fat mass: muscle, bone, organs and water together. These formulas estimate it from weight and height; the Body Fat Calculator estimates the complementary fat share by a circumference method.
Each is a published regression fitted to its own study population, and each is printed with its constants so its output can be reproduced. The page does not rank them; the spread between them is part of the information.
No. The page returns formula outputs for information only. It does not assess or advise any person, and health questions belong with a clinician.
No. The calculation runs entirely in the browser and nothing entered is uploaded, stored or tracked.
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