🏥 Clinical Drug Dosing Boer Formula (1984) Hume Formula (1966)
Lean Body Mass Calculator
Calculate your lean body mass (LBM) — the weight of everything in your body except fat. Used globally in medicine for drug dosing, sports science, and body composition assessment.
Quick Answer
LBM = Total Weight − Fat Mass. Most accurate if you know your body fat %: LBM = weight × (1 − BF%/100). Boer formula (1984) is the most widely used anthropometric estimate for clinical drug dosing. Average LBM: 75 kg man at 20% BF = 60 kg LBM. 60 kg woman at 28% BF = 43 kg LBM. This formula is used in ICUs, oncology, and anesthesia worldwide.
LBM in Clinical Practice by Country
| Country / System | LBM Formula Used | Key Application |
|---|---|---|
| 🇺🇸 USA — Clinical Pharmacology | Boer (1984) — preferred; Devine (1974) — legacy | Aminoglycoside dosing (gentamicin), vancomycin, chemotherapy agents |
| 🇬🇧 UK — NHS / BNF | Boer or Devine formula; depends on drug protocol | British National Formulary uses LBM for renal-dose drugs and ICU medications |
| 🇨🇦 Canada — Health Canada | Boer formula (same as US/UK) | Cancer chemotherapy dosing; anesthesia weight adjustment |
| 🇦🇺 Australia — SHPA | Boer formula; Janmahasatian for obese (BMI >40) | Society of Hospital Pharmacists Australia: LBM in drug dosing guidelines |
| 🇩🇪 Germany — AWMF | Boer / Janmahasatian for morbidly obese | German clinical guidelines specify IBW/LBM for gentamicin, vancomycin, heparin |
| 🇯🇵 Japan — JSCN | Boer formula used; Japan Society for Clinical Nutrition | Japan uses LBM in critical care nutrition and chemotherapy protocols |
| 🌍 WHO / Global Research | DEXA scan (gold standard) | DEXA used in nutrition research, sarcopenia screening, and cancer staging globally |
LBM Formula Comparison
| Formula | Used For | Inputs Required |
|---|---|---|
| Boer (1984) | Clinical drug dosing globally (most preferred) | Weight, height, sex |
| Hume (1966) | Earlier clinical use — still cited | Weight, height, sex |
| Body Fat Method | Most accurate when BF% is known | Weight + body fat % |
| Janmahasatian (2005) | Obese patients (BMI >40) | Weight, height, sex |
Frequently Asked Questions
How much muscle mass is normal? ▾
Average skeletal muscle mass (a subset of LBM) is approximately 38–54% of body weight in men and 28–39% in women (varies by age and fitness). By absolute mass: an average 75 kg male has roughly 32–38 kg of skeletal muscle. These values decline significantly with age and inactivity. Elite athletes can have 50%+ muscle mass. These reference values are similar across ethnic groups, though some research suggests slight differences in muscle distribution patterns.
How does lean body mass relate to drug dosing? ▾
Many medications are dosed based on LBM rather than total body weight to ensure accurate dosing in patients with high body fat. For example, aminoglycoside antibiotics (gentamicin, tobramycin) are dosed at 7 mg/kg LBM/day in the UK, Australia, and US. Some chemotherapy drugs, succinylcholine (anesthetic), and several cardiac medications use LBM-based dosing. The Boer formula is preferred over the older Devine formula in most modern clinical pharmacokinetics guidelines.
Sources & Methodology
Lean body mass is estimated with the Boer, James and Hume formulas from height and weight; results differ slightly by the population each formula was derived from.
Standards and figures reviewed 2026.