How to Calculate Lean Body Mass

Lean Body Mass (LBM) is the weight of everything in your body except fatβ€”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 Γ— weight in kg) + (0.267 Γ— height in cm) βˆ’ 19.2 Women: LBM = (0.252 Γ— weight in kg) + (0.473 Γ— height in cm) βˆ’ 48.3

James Formula

Men: LBM = 1.1 Γ— weight (kg) βˆ’ 128 Γ— [weight (kg) / height (cm)]Β² Women: LBM = 1.07 Γ— weight (kg) βˆ’ 148 Γ— [weight (kg) / height (cm)]Β²

Hume Formula

Men: LBM = (0.3281 Γ— weight in kg) + (0.3393 Γ— height in cm) βˆ’ 29.5336 Women: LBM = (0.2296 Γ— weight in kg) + (0.4229 Γ— height in cm) βˆ’ 43.2933

Step-by-Step Example (Boer)

Male, 80 kg, 178 cm tall: LBM = (0.407 Γ— 80) + (0.267 Γ— 178) βˆ’ 19.2 = 32.56 + 47.526 βˆ’ 19.2 = 60.9 kg

Body fat mass = 80 βˆ’ 60.9 = 19.1 kg β†’ 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)β€”you won't see this improvement if you only track the scale.

Use our lean body mass calculator for any of the three formulas.