Lean Body Mass (Boer) Calculator
Lean body mass (LBM) is your total weight minus fat mass: muscle, bone, organs and water. The Boer formula estimates LBM from weight, height and sex and is widely used in clinical and fitness settings, including drug dosing. Enter your weight, height and sex to estimate your lean body mass, fat mass and lean percentage. Because the Boer formula is sex-specific, choose the option that applies to you.
Boer formula
Male: LBM = 0.407 * weight(kg) + 0.267 * height(cm) - 19.2
Female: LBM = 0.252 * weight(kg) + 0.473 * height(cm) - 48.3
Fat mass = weight - LBM
The Boer (1984) equations estimate lean body mass from weight and height with separate constants by sex. Fat mass is the remainder after subtracting LBM from total weight.
Worked example
An 80 kg, 180 cm male: LBM = 0.407*80 + 0.267*180 - 19.2 = 32.56 + 48.06 - 19.2 = 61.42 kg. Fat mass = 80 - 61.42 = 18.58 kg. Lean percentage = 61.42 / 80 = 76.78 percent.
Frequently asked questions
What is the Boer formula used for?
The Boer formula estimates lean body mass for body composition tracking and, in clinical practice, for weight-based drug dosing where dosing on lean mass is more appropriate than total weight. It needs only weight, height and sex.
How does it differ from other LBM formulas?
There are several published LBM equations, including Hume and James, each with different constants. They give broadly similar results for typical adults but can diverge at extremes of size. Boer is one of the most commonly cited.
Is estimated LBM the same as measured?
No. The Boer formula is an estimate based on population averages. Direct methods such as DEXA scanning measure lean mass more precisely. Use the formula for convenient estimates and trends, not as a clinical measurement.
Sources
- U.S. National Institutes of Health (MedlinePlus): body composition measurement.
Reviewed by the CalculatorHub team, edited by James Graham, 19 June 2026. See our methodology.