Lean Body Mass Calculator
Estimate your lean body mass with the Boer, James, and Hume formulas, or calculate it exactly from your body fat percentage — in metric or imperial units.
Three Formulas, or a Direct Measurement
The Boer formula is the primary estimate — it tracks measured lean mass best for most adults. Enter your body fat percentage and the calculator switches to the direct value: weight × (1 − body fat ÷ 100), which always beats a formula estimate.
What Lean Mass Is Good For
Lean body mass drives protein targets and powers the Katch-McArdle BMR formula. Knowing it separates real muscle and organ tissue from fat mass when you track body composition.