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Your Measurements
Results (Boer Formula)
Body Composition Breakdown
Body Fat Categories (Men)
Note: This calculator uses the Boer formula (1984), which estimates lean body mass from weight, height and sex. Results are estimates and may differ from direct body-composition measurements (e.g. DEXA). Consult a healthcare professional for clinical assessments.
Your lean body mass (LBM) is the weight of everything in your body except fat — muscles, bones, organs and water. Knowing your LBM helps set realistic fitness goals, calculate accurate calorie needs and track true muscle gain over time. This free calculator uses the clinically validated Boer formula to estimate LBM from your weight, height and biological sex in seconds.
The Boer (1984) formula estimates lean body mass (LBM) from weight and height. For males: LBM = 0.407 × weight(kg) + 0.267 × height(cm) − 19.2. For females: LBM = 0.252 × weight(kg) + 0.473 × height(cm) − 48.3. It is widely used in pharmacokinetics and clinical medicine because it accounts for sex-based differences in body composition.
A healthy lean body mass percentage (the inverse of body fat %) is roughly 75–85% for men and 68–78% for women. Athletes tend toward the higher end of these ranges, while sedentary individuals may fall below them. Body composition goals vary by age, sport and individual health context.
In practice the two terms are often used interchangeably. Strictly speaking, fat-free mass (FFM) excludes all lipids, while lean body mass includes a small amount of essential fat (about 2–3%) stored in the brain, nerves and cell membranes. For most practical fitness and health purposes the difference is negligible.
Many medications — particularly anesthetics, antibiotics and chemotherapy agents — distribute mainly into lean tissue rather than fat. Dosing based on total body weight can lead to overdosing in obese patients. Clinicians use LBM to calculate safer, more accurate doses, which is why the Boer formula was originally developed.