Lean Body Mass Calculator
Estimate your lean body mass (everything except fat) using the Boer formula from your weight, height and sex.
Reviewed October 7, 2026 Runs in your browser — inputs are never stored
This tool provides general educational estimates only and is not medical advice. It does not diagnose, treat, or replace guidance from a qualified healthcare provider. Consult a doctor for decisions about your health.
About the Lean Body Mass Calculator
The lean body mass calculator estimates how much of your weight is not fat — muscle, bone, organs and water — using the Boer formula, which needs only your sex, weight and height. Subtracting lean mass from total weight gives an estimate of fat mass. Lean body mass is used in some medication dosing and nutrition plans, and tracking it over time shows whether weight changes come from fat or from muscle. Because it is a prediction from height and weight, it is less accurate for very muscular or very lean people than a body-composition scan.
How to use it
- 1Select your sex.
- 2Enter your weight and height.
- 3Press Calculate to see estimated lean body mass, fat mass and body fat percentage.
Worked example
a man weighing 75 kg and 178 cm tall has an estimated lean body mass of 0.407 × 75 + 0.267 × 178 − 19.2 ≈ 58.9 kg, leaving about 16.1 kg of fat mass, or roughly 21% body fat.
How it works
Boer formula
Men: LBM = 0.407·weight + 0.267·height − 19.2
Women: LBM = 0.252·weight + 0.473·height − 48.3
Who it is for
People tracking body composition and anyone setting protein targets based on lean mass.
Why it helps
It separates the part of your weight you usually want to keep from the part you may want to lose.
Common use cases
- Tracking body composition during a diet
- Basing protein intake on lean mass
- Comparing the result with a tape-measure body fat estimate
Frequently asked questions
A:It is your total body weight minus fat mass — muscle, bone, organs and water.
A:It is used to dose some medications and to track muscle retention during weight loss.
Reviewed for accuracy · Last updated October 7, 2026
Formulas follow recognised clinical references — including WHO BMI classifications, the Mifflin-St Jeor equation, and Naegele’s rule — and are periodically checked against published reference values.
CalcWisee Editorial Team
Calculator development and formula review
CalcWisee is an independent site founded by Ayman. Every calculator is built from a published formula or official definition, tested against hand-worked examples before it goes live, and corrected promptly when a reader reports an issue to ayman@calcwisee.com.
Expertise: Financial mathematics, Health and fitness formulas, Applied mathematics, Unit conversion standards
References & sources
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