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Lean Body Mass Calculator
Estimate your lean body mass (weight minus fat) using the Boer and James formulas, all computed in your browser.
HOW TO USE
- 1Pick your gender.
- 2Enter your weight in kg or lb and height in cm or ft.
- 3Read your lean body mass from Boer and James in the results, in kg and lb.
EXAMPLE
INPUT
Gender: Male · Weight: 80 kg · Height: 180 cm
OUTPUT
Boer: 61.4 kg · James: 62.7 kg
FAQ
What is lean body mass?
Lean body mass is everything in your body except fat, muscle, bone, organs and water. It is a useful baseline for nutrition and fitness planning.
Which formula is more accurate?
Boer is generally preferred in clinical use; James is older. Both estimate within a few kg of each other for most people. Neither measures your actual body composition directly.
Why don't the formulas use age?
The Boer and James formulas were derived from weight and height alone. Age-based adjustments exist in some newer methods, but they are not part of these classic equations.
How is this different from body fat percentage?
Body fat percentage tells you the share of fat in your body; lean body mass is the absolute weight of everything else. If you know your body fat %, you can compute LBM directly, this calculator estimates it without measurements.