Lean Body Mass Calculator
Estimate your lean body mass, fat mass and lean percentage from weight and height with the Boer formula.
How it works
Boer — men: LBM = 0.407×kg + 0.267×cm − 19.2 · women: 0.252×kg + 0.473×cm − 48.3
Lean body mass is your total weight minus body fat. The Boer formula estimates it from weight and height alone, which makes it handy when you don’t have a body-fat measurement. It’s a prediction from population averages, so someone unusually muscular or lean will read a bit off — a body-fat measurement pins it down better.
Worked example
A 170-lb (77.1 kg) man who is 5′9″ (175.3 cm): LBM = 0.407 × 77.1 + 0.267 × 175.3 − 19.2 ≈ 59.0 kg (130 lb), leaving about 40 lb of fat mass and a 76% lean fraction.
Frequently asked questions
What’s lean body mass good for?
It’s used for medication dosing, for setting protein targets, and as a dieting checkpoint — keeping lean mass steady while weight drops means you’re losing mostly fat.
Boer, James or Hume — which formula?
Boer is a well-validated general choice and the one used here. All estimate-only formulas agree within a few pounds for typical builds and drift apart at the extremes.
Can I gain lean mass and lose weight at once?
Beginners and people returning to training often can (“body recomposition”). For most experienced lifters, meaningful muscle gain and fat loss happen more easily in separate phases.
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General educational estimate, not medical advice. Talk to a doctor for anything about your health.