Lean Body Mass Calculator
Estimate your lean body mass and fat mass using the Boer formula.
Results update as you type.
About this calculator
A lean body mass (LBM) calculator estimates the weight of everything in your body that is not fat — muscle, bone, organs and water — from your height, weight and sex. It uses the Boer formula, a well-validated prediction equation, and reports the remaining fat mass and body-fat percentage alongside it.
Frequently asked questions
What is the Boer formula?
For men, LBM = 0.407 × weight(kg) + 0.267 × height(cm) − 19.2; for women, LBM = 0.252 × weight + 0.473 × height − 48.3. It predicts lean mass from height and weight and is one of the most accurate simple equations.
Why does lean body mass matter?
It sets your resting metabolism and drug-dosing in medicine, and tracking it helps confirm you are losing fat rather than muscle. Protein and calorie targets are often based on LBM rather than total weight.
Is this the same as body-fat percentage?
They are two sides of the same number: fat mass is your weight minus lean body mass, and body-fat percentage is fat mass divided by total weight. The tool shows all three.
Results are estimates for general guidance only, not financial, medical or tax advice.