What Is Lean Body Mass?
Lean body mass (LBM) is your total body weight minus fat mass — including muscle, bone, organs, and water. This calculator estimates LBM using height, weight, and sex through three commonly used formulas from clinical and sports science literature.
How to Use the Lean Body Mass Calculator
- Select your sex.
- Enter your weight and height.
- Compare estimates from three established formulas.
Lean Body Mass Formulas
Worked Example
Boer: 0.407 × 81.6 + 0.267 × 177.8 − 19.2 ≈ 61.5 kg ≈ 136 lb
This means an estimated body fat mass of roughly 44 lb (about 25%) for this example.
Understanding Your Results
Each formula uses slightly different coefficients derived from different population studies, so results vary a few pounds between them. Estimated Body Fat Mass is your total weight minus the average LBM estimate — a useful cross-check against body fat percentage calculators.
Why Lean Body Mass Matters
- Nutrition and medication dosing sometimes use LBM instead of total body weight for more precise calculations.
- Tracking LBM alongside weight helps distinguish muscle gain from fat gain (or loss) during a fitness program.
- LBM is more stable than total weight for people with fluctuating water retention or digestion-related weight changes.
Common Mistakes to Avoid
- Treating formula-based LBM estimates as exact — actual body composition testing (DEXA, BIA) is more precise.
- Confusing lean body mass with muscle mass specifically — LBM includes bone, organs, and water too, not just muscle.
- Comparing LBM across very different formulas without noting they use different underlying assumptions.
Frequently Asked Questions
It's your total body weight minus fat mass, including muscle, bone, organs, and body water.
No single formula is universally "best" — they're all estimates derived from different population studies. Direct measurement methods like DEXA scans are more precise than any formula.
Lean body mass includes all non-fat tissue (muscle, bone, organs, water), while muscle mass refers specifically to skeletal muscle tissue — LBM is always somewhat higher than muscle mass alone.
Yes — subtract LBM from total weight to estimate fat mass, then divide by total weight for an approximate body fat percentage.
Yes — strength training and adequate protein intake can increase lean body mass (primarily muscle) over time, which is one reason it's tracked alongside weight during a fitness program.