Lean Body Mass Calculator
Everything That Isn't Fat
Lean body mass covers muscle, bone, organs, and water — every tissue except stored fat. Two people can share an identical body weight and BMI while carrying very different amounts of lean mass, which is exactly why strength coaches and physique-focused dieters track LBM rather than weight alone: it's the mass that should generally be preserved (or built) while fat mass is what actually changes with a diet.
The Formula
Men: LBM (kg) = 0.407 × Weight(kg) + 0.267 × Height(cm) − 19.2
Women: LBM (kg) = 0.252 × Weight(kg) + 0.473 × Height(cm) − 48.3
Fat mass is then found by subtracting LBM from total body weight, and fat percentage is fat mass divided by total weight. The calculator clamps LBM between 0 and total body weight so an unusual input combination can't return a nonsensical result.
Where Lean Body Mass Matters
- Medication and anesthesia dosing — certain drug dosages are calculated from lean mass rather than total body weight, since fat tissue doesn't metabolize the same way.
- Setting protein targets — protein intake recommendations for athletes are often expressed per kg of lean mass rather than total weight, giving a more precise target for larger or leaner individuals.
- Tracking body recomposition — watching LBM hold steady (or rise) while total weight falls is a stronger sign of fat-specific loss than the scale number alone.
How to Use This Calculator
- Choose Metric (kg/cm) or Imperial (lb/in) units.
- Select your sex.
- Enter your weight.
- Enter your height.
- Select Calculate to see your estimated lean body mass, fat mass, and fat percentage.
Related Calculations
Compare this estimate against the Body Fat Calculator, or use your lean mass figure to set a target with the Protein Calculator.