Lean body mass calculator

Lean body mass (LBM) is your total weight minus your body fat. It includes muscle, bone, organs, skin and water. When you lose weight, the goal is to lose fat while keeping as much lean mass as possible.

We show three well-known formulas. Boer is generally the most accurate for adults, so we use it as the main result.

Boer (men): 0.407 × W + 0.267 × H − 19.2
Boer (women): 0.252 × W + 0.473 × H − 48.3
James (men): 1.1 × W − 128 × (W ÷ H)²
James (women): 1.07 × W − 148 × (W ÷ H)²
Hume (men): 0.32810 × W + 0.33929 × H − 29.5336
Hume (women): 0.29569 × W + 0.41813 × H − 43.2933
(W in kg, H in cm)

• Eat enough protein at every meal.
• Do strength training 2 to 3 times a week.
• Lose weight slowly, 0.25 to 1 kg a week.
• Track body composition, not just the scale.

Please keep these in mind before acting on your result:

• These formulas estimate lean mass from height and weight only. They don't measure it.
• They were developed in small, mostly Western groups of adults, so they're less accurate for very muscular, very heavy or older people, and may differ for Asian body types.
• The James formula gives unreliable (falling) results at high body weights.
• Lean mass includes muscle, bone, organs and water, so this can't tell you how much of it is muscle.

1. Boer P. Estimated lean body mass as an index for normalization of body fluid volumes in humans. Am J Physiol. 1984;247(4 Pt 2):F632–F636. Link
2. James WPT. Research on Obesity: a report of the DHSS/MRC group. London: HMSO; 1976.
3. Hume R. Prediction of lean body mass from height and weight. J Clin Pathol. 1966;19(4):389–391. Link