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Fat-Free Mass Compartment

Lean Body Mass (LBM) Calculator

Quantify your fat-free tissue compartment (skeletal muscle, bone, and organs) across three validated clinical models. Dual Imperial and Metric support.

Clinical LBM Estimation Engine

Real-time calculation • Dual US Imperial (lbs, ft/in) / Metric (kg, cm)

Adjusts gender-specific Lean Body Mass regression constants.
lbs
ft
in

LBM Estimates

Clinical Formulas
Consensus Lean Body Mass
127 lbs
Triangulated average of Boer, James, and Hume clinical formulas
Multi-Formula Breakdown:
Boer Formula (1984)
128 lbs
Standard in anesthesia dosing
James Formula (1976)
126 lbs
Classic non-linear model
Hume Formula (1966)
127 lbs
Linear anthropometric regression
Estimated Fat Mass
38 lbs
Non-lean tissue
Derived Body Fat %
23.0%
Formula consensus
Clinical Evidence & Methodology

Clinical Applications of Lean Body Mass (Fat-Free Mass)

Clinically Reviewed by Dr. Julian Vance, MD, FACP • Updated September 2026

1. What Comprises Lean Body Mass?

Lean Body Mass (LBM), often synonymous with Fat-Free Mass (FFM) in clinical practice, comprises all non-adipose physiological tissues: skeletal muscle, skeletal bone mineral matrix, visceral organs (heart, liver, kidneys, brain), and intracellular/extracellular water. LBM constitutes the primary metabolic driver of glucose disposal, basal thermal expenditure, and drug clearance in the human body.

2. Medical Utility in Chemotherapy & Anesthetic Dosing

Dosing narrow therapeutic index drugs based on Total Body Weight (TBW) in overweight or obese patients leads to supra-therapeutic plasma drug concentrations. The Boer and James formulas are widely integrated into critical care and anesthesiology protocols to determine target infusions of propofol, remifentanil, and neuromuscular blocking agents, preventing fatal overdoses and respiratory arrest.

3. Peer-Reviewed Citations

  1. Boer, P. (1984). Estimated lean body mass as an index for normalization of body fluid volumes in humans. American Journal of Physiology-Renal Physiology, 247(4), F632-F636. PMID: 6496691.
  2. James, W. P. T. (1976). Research on obesity: a report of the DHSS/MRC group. HMSO, London.
  3. Hume, R. (1966). Prediction of lean body mass from height and weight. Journal of Clinical Pathology, 19(4), 389-391. PMID: 5929341.
  4. Morgan, D. J., & Bray, K. M. (1994). Lean body mass as a predictor of drug dosage. Implications for drug therapy. Clinical Pharmacokinetics, 26(4), 292-307. PMID: 8013166.