Lean Body Mass Calculator
Estimate your lean body mass and fat mass using the Boer formula — a quick body-composition breakdown from just your sex, height, and weight.
Lean Body Mass Calculator
Enter your details to estimate lean mass and fat mass
Your Results
Complete the form to see your body composition
Lean mass, fat mass, and lean percentage
Lean body mass (LBM) is everything in your body that isn't fat: muscle, bone, organs, skin, and water. It is the metabolically active tissue that drives most of your daily calorie burn.
When you lose weight, the goal is usually to lose fat while preserving lean mass. Tracking LBM helps you judge whether your diet and training are actually protecting muscle.
- 1Set a protein target — roughly 1.6–2.2 g per kg of body weight — to support your lean mass during a cut.
- 2Resistance train — strength training is the strongest signal your body has to hold onto muscle while in a deficit.
- 3Recheck monthly — if lean mass is dropping faster than fat, your deficit may be too aggressive or protein too low.
Accuracy Note
The Boer formula is a validated population estimate, but true lean mass can vary by training history, hydration, and genetics. For precise measurement, use DEXA, hydrostatic weighing, or bioelectrical impedance. This tool is for educational purposes only.