Quick answer: lean body mass is your total weight minus fat mass, calculated using the Boer formula from your weight and height. Use our free Lean Body Mass Calculator for an instant estimate.
What Lean Body Mass Includes
Lean body mass includes muscle, bone, organs, and water — essentially everything except stored fat. It's a useful metric for tracking muscle gain independent of fat loss during a fitness program.
The Boer Formula
The Boer formula estimates LBM using weight and height, with separate equations for men and women, and is widely used in clinical and fitness settings for its balance of simplicity and accuracy.
Frequently Asked Questions
Why track lean body mass instead of just weight?
Weight alone doesn't distinguish muscle from fat — tracking LBM shows whether you're gaining muscle or losing fat during training.
Is this the same as fat-free mass?
Yes, lean body mass and fat-free mass are generally used interchangeably.
How accurate is a formula-based estimate?
It's a reasonable estimate; body composition scans (DEXA, bioelectrical impedance) are more precise but less accessible.
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