Lean Body Mass Calculator
Calculate your Lean Body Mass (fat-free mass) using three established formulas — Boer, James and Hume — to get a reliable range.
What Does This Tool Do?
Calculate lean body mass (LBM) — the weight of everything in your body except fat — using three clinical formulas: Boer, James and Hume. Shows fat mass and estimated body fat percentage too.
Key Features
3 Formulas
Boer, James and Hume compared side by side.
Fat Mass
Fat mass shown for each formula.
Body Fat %
Estimated body fat percentage.
Instant
Immediate results.
How to Use
- Enter your weight in kg.
- Enter your height in cm.
- Select your sex.
- Click Calculate LBM.
Frequently Asked Questions
What is Lean Body Mass?▾
LBM is total body weight minus fat mass — it includes muscle, bone, organs, skin, blood and water. Also called fat-free mass (FFM).
Why three formulas?▾
Each formula was developed using different study populations and measurement methods. Comparing all three gives a more reliable estimate than any single formula alone.
How is body fat % estimated?▾
Body Fat % = (Weight − LBM) / Weight × 100. This uses the average LBM from the three formulas.