Lean Body Mass Calculator

How to Calculate Lean Body Mass

Lean Body Mass (LBM) is your total weight minus body fat — everything that is not fat: muscle, bones, organs, water, and blood. This calculator uses the U.S. Navy body circumference method.

Step-by-step

1. Select your biological sex.
2. Enter your weight in pounds.
3. For men: enter waist circumference at the navel.
4. For women: enter waist (narrowest), wrist, hip (widest), and forearm measurements.
5. The calculator estimates your LBM and body fat percentage.

Worked example

Male, 180 lbs, 34" waist: LBM ≈ 154.3 lbs, body fat ≈ 14.3%. This means about 25.7 lbs of body fat and 154.3 lbs of lean mass.

Why LBM matters

LBM is a better health indicator than BMI alone. Two people with the same weight and BMI can have very different body compositions. Higher LBM (more muscle) means higher metabolism and better health outcomes. Track LBM over time to see if weight changes are from muscle gain or fat loss.