What is lean body mass?
LBM is total body weight minus fat mass. It includes muscle, bone, organs, and water.
Lean Body Mass Calculator
Estimate lean body mass (LBM) with the Boer equation or derive it from weight and body fat percentage.
Calculate lean body mass
Pick a method, enter sex, height, and weight. Add body fat % if using that mode.
About this calculator
How to use Lean Body Mass Calculator, plus the formulas and logic behind the results.
Tool description
Lean body mass is everything in your body that is not fat—muscle, bone, organs, and water. This tool uses the Boer formula or a simple fat-subtraction method.
How to use
- Choose Boer formula or body fat % mode.
- Enter sex, height, and weight.
- If using body fat mode, enter your estimated body fat percentage.
- Review LBM, fat mass, and fat-free percentage.
Formulas & reference
Men (Boer): LBM = 0.407×weight + 0.267×height − 19.2Women (Boer): LBM = 0.252×weight + 0.473×height − 48.3From BF%: LBM = weight × (1 − BF%÷100)Fat mass = weight − LBM
What LBM includes
- Skeletal muscle
- Bone mineral content
- Organs and connective tissue
- Body water (non-fat component)
Calculation logic
Boer uses sex-specific linear equations with weight in kg and height in cm. Body-fat mode subtracts estimated fat mass directly from total weight.
Boer and similar equations are population averages. Hydration and training status affect day-to-day LBM estimates.
Lean Body Mass Calculator FAQ
Common questions about this calculator and how to use the results.
Boer vs body fat mode—which is better?
If you have a reliable body fat reading (DEXA, calipers), body fat mode is often closer. Boer is handy when you only know height and weight.
Are the units important?
Yes. Boer expects kg and cm internally; the calculator converts US units automatically.
Can LBM exceed body weight?
No. If your body fat % is invalid, the tool will ask you to fix it.
Does this measure muscle only?
No. LBM is broader than muscle—it includes bone, organs, and water too.
How often should I recalculate?
Track monthly if you are changing training or diet; daily swings mostly reflect water weight.