Body Composition
Lean Body Mass Calculator
Estimate your lean body mass and fat mass from height, weight, and sex using the widely used Boer formula.
How to Read Your Result
Lean body mass (LBM) is everything in your body that is not fat - muscle, bone, organs, and water. If body fat percentage is entered, LBM is calculated directly as weight x (1 - body fat). Otherwise, the calculator uses the Boer formula from height, weight, and sex.
Resistance training and adequate protein help preserve LBM during fat loss.
LBM is useful for setting protein targets and tracking muscle retention.
For precise body composition, use DEXA, BodPod, or skilled skinfold testing.
Calculate LBM with body fat percentage
When you know body fat percentage, lean body mass equals body weight multiplied by the non-fat percentage. For example, 80 kg at 20% body fat gives 64 kg of lean body mass.
Boer formula for lean body mass
If body fat is unknown, the Boer formula estimates LBM from height, weight, and sex. This is useful for a starting estimate, but direct body-composition measurements are better for tracking small changes.
Frequently Asked Questions
What is lean body mass?
Lean body mass is your total weight minus fat mass: muscle, bone, organs, and body water combined.
Why does lean mass matter?
It drives metabolism and strength. Preserving lean mass during weight loss keeps results healthier and more sustainable.
How accurate is the Boer formula?
It is a solid population estimate from height, weight, and sex, but individual results vary. Body scans are more precise.
How do I calculate lean body mass with body fat?
Multiply body weight by one minus body fat as a decimal. At 20% body fat, multiply weight by 0.80.