Health & Fitness
Use the Boer formula to estimate your lean body mass from height and weight.
Lean Body Mass
58.1kg
128.0 lb
Lean body mass includes muscle, bone, organs, and water. The Boer formula provides an estimate based on sex, height, and weight.
Lean Body Mass (LBM) is the total weight of everything in your body except fat—your muscles, skeleton, organs, and water. It's calculated by subtracting your estimated body fat weight from your total body weight. LBM is crucial because muscle is metabolically active (burns calories), whereas fat is not, so knowing your LBM helps you understand your metabolism and fitness progress better than weight alone.
The calculator uses your body weight, height, age, and sex, combined with a body fat percentage estimate (either provided by you or calculated using standard formulas like Katch-McArdle or Jackson-Pollock). From that, it estimates your total body fat weight in pounds or kilograms, then subtracts it from your total weight to give your LBM. The result is typically expressed in kilograms or pounds.
LBM (kg) = Body Weight (kg) × (1 − Body Fat %) or LBM (kg) = Body Weight (kg) − Fat Mass (kg)Body Weight is your total mass on a scale. Body Fat % is your estimated or measured percentage of total body weight that is fat tissue. The formula assumes the remainder is lean mass (muscle, bone, organs, water). Fat Mass is calculated from your body fat percentage, then subtracted to isolate lean tissue.
| Input | Result | Notes |
|---|---|---|
| Male, 85 kg, 25% body fat | LBM = 63.75 kg; Fat Mass = 21.25 kg | A 85 kg person with 25% body fat carries about 64 kg of muscle and bone, meaning diet and strength training target that 64 kg base for metabolism. |
| Female, 65 kg, 28% body fat | LBM = 46.8 kg; Fat Mass = 18.2 kg | Even with a lower overall weight, LBM of 47 kg is substantial; her calorie needs are driven more by that lean mass than the 18 kg of fat. |
| Male, 90 kg, 15% body fat (athletic) | LBM = 76.5 kg; Fat Mass = 13.5 kg | Athletes often have higher LBM; this person's metabolic rate and calorie burn are much higher than someone at 90 kg with 30% body fat. |
LBM is metabolically active—your muscles, organs, and bones burn calories even at rest. Knowing your LBM helps you set realistic calorie needs, design effective diets, and track whether you're building or losing muscle, which is far more useful than weight alone.
No. LBM includes muscle (~80%), bone, organs, and water. Actual muscle mass is roughly 80% of LBM. If you specifically want muscle mass, multiply LBM by 0.8 for an estimate, but true muscle mass requires advanced testing.
Recalculate every 8–12 weeks if you're actively training or dieting. Your body fat % and LBM change with training, so a fresh calculation keeps your nutrition and goals aligned with reality.
Healthy ranges: men 15–25%, women 20–30%. Athletes are lower (men 10–15%, women 15–20%). Very low (<8% men, <15% women) is hard to sustain and can harm health. Aim for consistency and feeling good, not a number.
Best methods: DEXA scan (most accurate), hydrostatic weighing, or bioelectrical impedance. Quick estimates: online calculators (waist/hip measurements), calipers, or smart scales. Each has margins of error—consistency matters more than precision.
Yes. Calculate your BMR (Basal Metabolic Rate) using your LBM or total weight, then multiply by activity level (1.2–1.9) to get TDEE (Total Daily Energy Expenditure). Your TDEE is your calorie maintenance—eat below it to lose fat, above it to gain.