Calculate your lean body mass — everything except fat. Get fat mass breakdown, protein targets and fitness benchmarks instantly.
Lean Body Mass (LBM) is the total weight of your body minus all fat tissue. It includes muscles, bones, organs, blood, water and other non-fat tissues. LBM is a critical measurement for calculating accurate protein requirements, medication dosing, athletic performance targets and overall metabolic health assessment.
LBM is more relevant than total body weight for many health and performance metrics. Protein requirements are based on lean mass, not total weight. Basal metabolic rate is primarily driven by lean mass. Exercise prescriptions for optimal muscle gain target lean mass. Even certain medications (like chemotherapy agents) are dosed based on LBM rather than total body weight.
| Component | % of LBM | Function |
|---|---|---|
| Skeletal Muscle | ~45% | Movement, metabolism |
| Skeleton (Bones) | ~15% | Structure, mineral storage |
| Organs | ~15% | Vital functions |
| Blood | ~7% | Transport |
| Other tissues | ~18% | Connective, skin, etc. |
LBM is the "lean" component the Ponderal Index aims to normalize. High lean mass with low fat mass is the ideal composition. Athletes typically have higher LBM relative to body weight, which is why standard BMI overestimates their adiposity.
Enter your weight, height and gender. The calculator computes LBM using two validated formulas (Boer and James) and averages them. Results include fat mass, body fat percentage estimate and daily protein target based on LBM.
Without an actual body fat measurement (e.g., DEXA), LBM is estimated from height and weight. Accuracy is approximately ±3–5 kg compared to gold-standard methods. Fluid retention, muscle mass variation and age-related muscle loss affect accuracy.