How it works
Lean body mass (LBM) is everything in your body except fat: muscle, bone, organs, skin and water. It is used in some medication dosing and in metabolic equations such as Katch-McArdle.
The Boer formula (1984) predicts LBM from height and weight and is considered among the more accurate of the simple equations for adults with average builds. The James (1976) and Hume (1966) formulas are shown for comparison.
Because these equations use only height and weight, they cannot tell a muscular person from someone of the same size with more fat. A body-fat measurement gives a more personal estimate. Results are estimates, not medical advice.
Formula
Boer: men LBM = 0.407 × kg + 0.267 × cm − 19.2; women LBM = 0.252 × kg + 0.473 × cm − 48.3
Questions people ask
What is the difference between lean body mass and muscle mass?
Muscle is only part of lean mass. LBM also includes bones, organs, skin, blood and body water, so it is always considerably larger than muscle mass alone.
What percentage of body weight is lean mass?
For many adults it is roughly 70–85% for men and 60–75% for women, depending on body fat level.
Why does the James formula give odd results at high weights?
The James formula includes a squared term that makes it fall off sharply at high weight-to-height ratios, which is why Boer is generally preferred.