Calculate your lean body mass (muscle, bone, organs — everything except fat) using the Boer formula.
This tool estimates your lean body mass (LBM) — the weight of your body excluding fat, including muscle, bone, organs, and water — based on your height, weight, and sex. LBM is used in fitness tracking, medication dosing, and understanding body composition beyond just total weight.
This calculator commonly uses the Boer formula: for men, LBM = (0.407 × weight in kg) + (0.267 × height in cm) − 19.2. For women, LBM = (0.252 × weight in kg) + (0.473 × height in cm) − 48.3.
Enter your height, weight, and sex, and the calculator returns your estimated lean body mass along with the corresponding estimated fat mass.
Example: A man who is 180 cm tall and weighs 80 kg has an estimated LBM of (0.407 × 80) + (0.267 × 180) − 19.2 ≈ 61.6 kg.
How is lean body mass different from body fat percentage? Lean body mass is expressed as an absolute weight (like kg or lb), while body fat percentage shows the proportion of your total weight that is fat — the two are related but measured differently.
Why is lean body mass useful for fitness tracking? It helps distinguish whether weight changes over time come from gaining or losing muscle versus fat, offering a more meaningful picture of progress than total body weight alone.
Is this formula accurate for athletes with high muscle mass? Formula-based estimates can be less precise for very muscular individuals compared to direct measurement methods like DEXA scans or bioelectrical impedance, which measure body composition more directly.
Why is lean body mass used in medication dosing? Some medications, particularly those that don't distribute into fat tissue, are dosed based on lean body mass rather than total body weight for more accurate, safer dosing.
Can lean body mass change over time? Yes, resistance training tends to increase lean body mass (through muscle growth), while prolonged inactivity or aging can gradually decrease it if not counteracted with exercise.