Medical & Clinical
Lean Body Mass Calculator
Your scale gives one number. Your body is really two: fat, and everything else that keeps you alive.
Lean body mass is total weight minus fat mass — muscle, bone, organs, and water. For example, an 80 kg person at 15% body fat carries 68 kg of lean mass. Lean tissue does nearly all the metabolic work of the body.
LBM = weight × (1 − body fat %).
Muscle ≈ 50–60% of lean mass.
LBM drives BMR and strength.
Calculate Your Lean Body Mass
Your Lean Body Mass
What Is Lean Body Mass?
Body composition is a two-part ledger: fat mass and lean body mass — everything else. Lean mass includes skeletal muscle, bone, organs, blood, and body water.
Lean tissue is metabolically expensive: it is why two people of the same weight can burn very different calories at rest, and why preserving it is the entire point of smart fat loss.
How It Is Calculated
Lean mass = weight × (1 − body fat % ÷ 100)
Example: Example: 80 kg at 18% → 65.6 kg lean mass (82% of body weight)
What lean mass contains (approximate)
| Component | Share of lean mass |
|---|---|
| Water | ~73% |
| Muscle | ~50–60% |
| Bone | ~15–17% |
| Organs & other | ~10–15% |
Limitations
- Component splits are population averages, not measurements.
- Lean mass includes water — hydration shifts the number day to day.
- Body-fat input quality decides the output quality.
Sources & Review
References used for this calculator’s formulas and thresholds:
Lean Body Mass FAQ
What is a healthy lean body mass?
There is no single number — it scales with height, sex, and training. Tracking your own lean mass over time is the meaningful metric.
How do I increase lean body mass?
Progressive resistance training + 1.6–2.2 g/kg protein + adequate sleep. Muscle is the lever you control.
Why does lean mass matter for weight loss?
Lean mass is your metabolic engine — losing it slows calorie burn. Slow deficits plus strength training protect it.
Important disclaimer: Results are educational estimates, not a substitute for professional medical advice. Discuss your results with a qualified professional before making decisions.