Lean body mass (LBM) is your body weight minus fat — muscles, bones, organs and water. It is one of the most meaningful metrics for fitness and health.
Unlike body weight alone, LBM shows how much "functional" mass you carry. Athletes with high muscle mass have a high LBM even if their BMI appears elevated.
The Three Scientific Formulas
Three established formulas exist for calculating lean body mass — each with a slightly different approach:
Boer Formula (1984)
Based on weight and height — simple and widely used.
James Formula (1976)
Accounts for the weight-to-height ratio — more sensitive to overweight.
Hume Formula (1966)
One of the oldest formulas, derived from cadaver measurements — more conservative estimates.
W = weight in kg, H = height in cm
Typical Reference Values
| Profile | Weight | LBM (avg) | LBM % |
|---|---|---|---|
| Male, 180 cm, active | 80 kg | ~61 kg | ~76% |
| Female, 165 cm, active | 60 kg | ~44 kg | ~74% |
| Male, 175 cm, athlete | 75 kg | ~58 kg | ~77% |
Calculate your lean body mass now
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Calculate for free now →Why LBM Matters More Than Body Weight
Two people with the same weight can have very different health profiles. Regular training builds muscle mass — weight rises, but LBM rises too. That is a positive sign.
Conversely, losing weight without training means losing not just fat but also muscle. LBM drops — a warning sign that body weight alone does not reveal.
Combine LBM with your body fat percentage for a complete picture of your body composition.
Conclusion
Lean body mass is a more precise metric than body weight. Use our Lean Body Mass Calculator and complement the result with the Body Fat Calculator and the BMI Calculator.
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