By ToolzHive
About this tool
Lean body mass (LBM) is everything in your body except fat: muscles, bones, organs, skin and water. This calculator estimates it from your height, weight and sex with three published formulas, Boer, James and Hume, and shows the body fat percentage each implies. Knowing your lean mass helps with protein targets, the Katch–McArdle BMR formula and tracking muscle as you train.
How to use Lean Body Mass Calculator
- Choose metric or imperial units and select your sex.
- Enter your height and weight.
- Compare the lean body mass from each formula. The Boer formula is shown first because it is generally the most accurate.
Worked example
A man who is 175 cm tall and weighs 70 kg has a lean body mass of about 56 kg with the Boer formula, meaning roughly 14 kg (20%) of his weight is fat.
Which lean body mass formula is best?
Studies generally find the Boer formula the most accurate of the three for adults. The James formula can give unrealistic results at very high body weights.
How can I measure lean body mass directly?
DEXA scans, bioelectrical impedance scales and hydrostatic weighing measure body composition directly. A tape-measure body fat estimate is a good free alternative.
Why does lean body mass matter?
Muscle burns more energy than fat and supports strength, balance and metabolic health. Keeping lean mass while losing fat is the goal of most healthy weight-loss plans.
Put this guide into practice
- Lean Body Mass Calculator — Calculate your lean body mass with the Boer, James and Hume formulas.