Calculate your estimated Lean Body Mass (muscle, bone, water, organs, and essential tissue), Fat Mass, and Body Fat Percentage using validated clinical equations with pediatric support.
| Formula & Model | Lean Body Mass (lbs / kg) | LBM Percentage | Fat Mass (lbs / kg) | Body Fat % |
|---|---|---|---|---|
Boer Formula (1984) Gold standard in clinical pharmacology & MRI correlation | 133.7 lbs (60.6 kg) | 76.4% | 41.4 lbs (18.8 kg) | 23.6% |
James Formula (1976) Widely used in anaesthesia & pharmacokinetic dosing | 136.4 lbs (61.9 kg) | 77.9% | 38.6 lbs (17.5 kg) | 22.1% |
Hume Formula (1966) Classic total body water & anthropometric model | 125.5 lbs (56.9 kg) | 71.7% | 49.6 lbs (22.5 kg) | 28.3% |
Understanding the physiological difference between Lean Body Mass, Fat-Free Mass, and its critical role in clinical pharmacology and athletic training.
Lean Body Mass consists of everything in your body except adipose fat tissue. It encompasses skeletal muscle mass (~40–50%), bone mineral density (~15%), organ tissues (liver, kidneys, brain, heart), body water (~60–70% of LBM), and glycogen stores.
While often used interchangeably, Lean Body Mass (LBM) includes essential cellular structural lipids (~3% in men, ~12% in women) found in cell membranes and the central nervous system. Fat-Free Mass (FFM) strictly excludes 100% of all lipid molecules.
Hydrophilic medications (such as intravenous anesthetics, aminoglycoside antibiotics, and chemotherapy agents) distribute primarily into lean tissue rather than adipose tissue. Indexing drug dosages to LBM avoids toxic overdose in obese patients.
Key clinical questions regarding Boer, James, and Hume formulas and healthy LBM ranges.
Anthropometric equations estimate Lean Body Mass based on population statistical regression. Direct clinical measurement methods such as Dual-Energy X-Ray Absorptiometry (DEXA), hydrostatic underwater weighing, or multi-frequency bioelectrical impedance analysis (BIA) may provide more individualized assessment. Always consult a healthcare provider for clinical pharmaceutical dosing.