How to Calculate Lean Body Mass
Lean Body Mass (LBM) is the weight of everything in your body except fat—muscles, bones, organs, blood, and fluids. It's a more useful metric than total body weight for guiding protein intake, calculating drug doses, and tracking true fitness progress.
LBM Formulas
Boer Formula (Most Accurate)
Men: LBM = (0.407 × weight in kg) + (0.267 × height in cm) − 19.2 Women: LBM = (0.252 × weight in kg) + (0.473 × height in cm) − 48.3
James Formula
Men: LBM = 1.1 × weight (kg) − 128 × [weight (kg) / height (cm)]² Women: LBM = 1.07 × weight (kg) − 148 × [weight (kg) / height (cm)]²
Hume Formula
Men: LBM = (0.3281 × weight in kg) + (0.3393 × height in cm) − 29.5336 Women: LBM = (0.2296 × weight in kg) + (0.4229 × height in cm) − 43.2933
Step-by-Step Example (Boer)
Male, 80 kg, 178 cm tall: LBM = (0.407 × 80) + (0.267 × 178) − 19.2 = 32.56 + 47.526 − 19.2 = 60.9 kg
Body fat mass = 80 − 60.9 = 19.1 kg → Body fat % = 19.1/80 = 23.9%
Why LBM Matters
Protein intake: Recommendations based on LBM are more precise than total body weight, especially for people with high body fat. Many experts suggest 1.6–2.2 g of protein per kg of LBM for muscle building.
Drug dosing: Anesthetics, certain antibiotics, and other medications are often dosed by LBM because fat tissue doesn't metabolize drugs the same way as lean tissue.
Tracking progress: LBM may increase while total weight stays flat (recomposition)—you won't see this improvement if you only track the scale.
Use our lean body mass calculator for any of the three formulas.