Calculate lean body mass and fat-free mass using the Boer, James, and Hume formulas.
Lean Body Mass Calculator turns sex, body weight, and height into separate estimates from the Boer, James, and Hume equations. Comparing all three shows how established weight-height formulas can differ for the same person. The main interpretation trap is the phrase "lean mass": the result is not skeletal muscle mass. It is a broader modeled quantity encompassing muscle together with body water, bone, organs, and other non-fat components.
A concrete input and expected output from the current implementation.
Input
Sex: male Weight: 80 kg Height: 180 cm
Expected output
Boer: 61.42 kg James: 62.72 kg Hume: 57.79 kg
For W = 80 and H = 180, the formulas produce 61.42, 62.716049..., and 57.7866 kilograms, respectively. Rounding each result to two decimal places gives the displayed values.
All three equations require body weight W in kilograms and height H in centimeters, plus the male or female coefficient set. Unit choice matters because the coefficients are tied to those units. Pounds and inches must be converted before calculation; inserting those numbers unchanged would produce an invalid estimate.
For males, Boer is 0.407W + 0.267H - 19.2, James is 1.1W - 128(W/H)^2, and Hume is 0.32810W + 0.33929H - 29.5336. For females, the corresponding equations are 0.252W + 0.473H - 48.3, 1.07W - 148(W/H)^2, and 0.29569W + 0.41813H - 43.2933. Results are in kilograms.
Each equation has its own coefficients and sex-specific form, so it maps the same height and weight to a different estimate. That spread is expected, as the worked example demonstrates. Use the equation named by your protocol or downstream calculation. If none is specified, this calculator cannot establish which estimate is biologically correct for you.
No. It predicts a broad lean-body quantity from height and weight; it does not observe skeletal muscle directly. A lean-mass result includes contributions from water, organs, bone, and other non-fat material. Measuring muscle specifically requires a suitable body-composition assessment, and this calculator cannot substitute for one.
The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
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