Lean Body Mass Calculator
Enter valid height and weight.
Lean body mass is everything that isn't fat — muscle, bone, organs, water. It's useful for setting protein targets and for the Katch-McArdle BMR formula, which is more accurate than weight-based formulas for people who know their lean mass.
Free lean body mass calculator using the Boer formula — a quick estimate of your fat-free mass from height, weight, and sex, no body fat percentage measurement required.
How it works
- Enter your sex, height, and weight
- See your estimated lean body mass and fat mass
Frequently asked questions
Why estimate lean body mass without a body fat measurement?
The Boer formula estimates lean mass from height, weight, and sex alone, using population averages — it's a fast estimate when you don't have a body fat percentage from a DEXA scan or calipers. If you do know your body fat %, a direct calculation (weight × (1 - body fat%)) will be more personalized.
What is lean body mass used for?
It's commonly used to set protein intake targets (often expressed per kg of lean mass) and as an input to the Katch-McArdle BMR formula, which tends to be more accurate than weight-based formulas for people who know their body composition.
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Update history
- 2026-09-03 Height and weight are now sliders instead of number fields, and the sex toggle shows an icon for each option.
- 2026-09-01 Added: a cover image — used as the card thumbnail, social share image, and blog title image.
- 2026-09-01 Launched: lean body mass calculator using the Boer formula. Entirely client-side, reuses the body composition engine.