Lean Body Mass Calculator
Estimate how much of your weight is lean tissue - muscle, bone, organs and water - using four published formulas, plus your lean mass percentage of total body weight.
Boer formula
56 kg
James formula
56.5 kg
Hume formula
52.8 kg
Lean mass percentage
80% of body weight
How to Use the Lean Body Mass Calculator
- Enter your sex, height and body weight in metric or imperial units.
- Optionally provide a body fat percentage for a more direct calculation.
- Compare the Boer, James, Hume and BMI-method lean mass estimates.
Formulas Used
Boer (men): LBM = 0.407×kg + 0.267×cm − 19.2 | women: 0.252×kg + 0.473×cm − 48.3
James (men): LBM = 1.1×kg − 128×(kg/cm)² | women: 1.07×kg − 148×(kg/cm)²
Hume (men): LBM = 0.32819×kg + 0.33929×cm − 29.5336 | women: 0.29569×kg + 0.41813×cm − 43.2933
From body fat: LBM = weight × (1 − BF%)
Frequently Asked Questions
What counts as lean body mass?
Everything that is not fat: skeletal muscle, smooth muscle, bone, blood, skin, organs and body water. It is also called fat-free mass, although essential fat inside organs makes the two technically slightly different.
Why does lean body mass matter?
Lean tissue drives resting metabolism, determines drug dosing in clinical settings, and is what strength training aims to preserve or grow during a calorie deficit.
Which formula should I trust?
If you know your body fat percentage from DEXA or a good measurement, computing LBM directly from it beats all prediction equations. Otherwise the Boer formula tends to perform well across body sizes.
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