What this tool does
Three published anthropometric equations estimate lean mass from sex, height, and weight. Protealpes averages them for a headline and still shows each one, because they disagree and that disagreement is the point.
How it works
Boer (1984) is often used in physiology indexing. James and Hume are older height-weight fits used in clinical estimation. All assume an average composition for a given size. A very muscular or very high-fat body will fool them in opposite directions.
Formula and methodology
Boer: men 0.407×kg + 0.267×cm − 19.2; women 0.252×kg + 0.473×cm − 48.3. James: men 1.1×kg − 128×(kg/cm)²; women 1.07×kg − 148×(kg/cm)². Hume: men 0.32810×kg + 0.33929×cm − 29.5336; women 0.29569×kg + 0.41813×cm − 43.2933. Headline LBM is the mean of the three. Limits: no waist, no age, no scan.
How to interpret the result
Use LBM to sanity-check a Navy tape lean-mass split or to think about protein per kg lean if you already distrust scale weight. Do not rank athletes by Boer. If Boer and Hume differ by a lot, you are looking at equation noise, not a new organ.
Example
80 kg, 180 cm man: Boer 61.4 kg, James 62.7 kg, Hume 57.8 kg, average 60.6 kg. FFMI from that lean mass sits in a normal trained neighborhood, not a comic-book score. Compare to Navy lean mass if you also taped; they will not match perfectly.
Common mistakes
- Calling the average “my DEXA.”
- Dosing drugs from a website LBM — these pages are not a pharmacy.
- Assuming the highest of the three is the flattering truth.
- Using LBM from last year after a 12 kg cut.
When this estimate may be off
- Body composition far from population averages.
- Edema, pregnancy, or casting that changes weight without lean tissue.
- You need FFM for a research protocol.
- Height measured with shoes or a slouch.