Lean Body Mass Calculator
Estimate your lean (fat-free) mass and fat mass from height and weight
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Quick summary
Enter your sex, height, and weight to estimate lean body mass (LBM) — everything that isn't fat, including muscle, bone, organs, and water — using the Boer formula. A 180 cm, 80 kg man has an estimated LBM around 61 kg, with about 19 kg of fat mass (~23% body fat). LBM is useful for setting protein targets, medication dosing, and tracking body composition, though direct methods like DEXA are more accurate.
Reviewed by Simple Calculators TeamLast reviewed
For information only — not medical advice. Results are estimates from published formulas and can't account for your health history. Talk to a doctor or other qualified clinician before making health decisions.
How to use this calculator
- Enter the inputs requested by the calculator.
- Choose the units or options that match your situation and review the assumptions.
- Run or update the calculation to see the result.
- Review the result, breakdown, and formulas shown on the page.
- Check the inputs, units, dates, and limitations before saving or sharing the result.
Frequently asked questions
What is lean body mass?
Lean body mass (LBM) is your total body weight minus fat — it includes muscle, bone, organs, connective tissue, and body water. It's sometimes called fat-free mass. Knowing your LBM helps set protein and calorie goals and is used clinically for dosing some medications.
How is lean body mass calculated?
This calculator uses the Boer formula, which estimates LBM from height and weight with sex-specific coefficients: for men, LBM = 0.407 × weight(kg) + 0.267 × height(cm) − 19.2; for women the coefficients differ. It's a validated estimate, not a direct measurement.
What is the difference between lean body mass and muscle mass?
Muscle is only part of lean body mass. LBM also includes bone, organs, and the large amount of water in the body, so it's considerably higher than muscle mass alone. Building muscle raises LBM, but LBM isn't a pure muscle measurement.
How accurate is a lean body mass estimate?
Formula-based estimates like Boer are reasonable for the general population but can't account for your individual build or fat distribution. For accuracy, direct body-composition methods — DEXA scans, hydrostatic weighing, or bioelectrical impedance — measure fat and lean mass rather than estimating from height and weight.
Key terms
- Lean Body Mass
- Total weight minus fat — muscle, bone, organs, and water.
- Boer Formula
- A height/weight equation for estimating LBM.
- Fat Mass
- Body weight minus lean body mass.
- Body Composition
- The proportion of fat to lean tissue in the body.
Methodology, sources & limitations
This page shows the formula, assumptions, and limitations used for this estimate. Rates, thresholds, and other time-sensitive inputs can change, so verify them against the relevant official source before relying on a result.
For our review approach and the primary sources we consult, see the methodology and source policy. If you spot an outdated figure or formula, please contact us with a correction.