Health & Fitness · Body Composition
Lean Body Mass Calculator — Boer, James, Hume or Body-Fat %
Estimate your lean body mass — muscle, bone, organs and water, everything except fat — from your sex, height and weight using the Boer, James and Hume formulas side by side, or directly from a measured body-fat percentage. Also shows the implied fat mass and body-fat percentage.
Your inputs
Quick start — try a typical case
Your result Live
Lean Body Mass
58.0 kg
77.4% of your 75.0 kg — Boer (1984)
- Fat Mass
- 17.0 kg
- Implied Body Fat
- 22.6%
All three formulas
3 rowsThese formulas were fitted to average adults; very muscular or very lean people get less accurate results. A DEXA scan measures lean mass directly.
Population-average estimates for healthy adults, not medical advice. Talk to a doctor or registered dietitian before major changes to diet or exercise, or if you are pregnant or have a health condition.
How this is calculated
Boer: men 0.407W + 0.267H − 19.2, women 0.252W + 0.473H − 48.3 · James: men 1.1W − 128(W/H)², women 1.07W − 148(W/H)² · Hume: men 0.32810W + 0.33929H − 29.5336, women 0.29569W + 0.41813H − 43.2933 · From body fat: W × (1 − BF%)
- W, H
- Weight in kg, height in cm
Lean body mass is your weight minus your fat. The Boer, James and Hume equations estimate it from height and weight using regressions measured on adults; Boer's is usually closest for most people, while James's can underestimate in people with obesity. If you know your body-fat percentage, the subtraction is direct.
Assumptions & sources
- Adults; formulas give population averages.
- 1Lean body weight-tailored iodinated contrast injection in obese patients: Boer versus James formula — BioMed Research International (PMC6110034)
- 2Lean body mass calculator (Boer, James and Hume formulas) — Pearson
Calculator ID HLTH-LBM-001 · version 1.0.0
Common questions
What is a good lean body mass?
It depends on height and sex; more useful is body-fat percentage — for men about 10–20 % and for women about 18–28 % is typical for healthy, active adults.
Which formula should I use?
Boer is generally closest for adults of ordinary build. If you've measured body fat, use that instead.
Is lean body mass the same as muscle?
No — it includes bone, organs, skin and water as well as muscle.