Lean Body Mass Calculator
Estimate lean body mass (LBM) using height, weight, sex, and the selected supported formula. Use results for dosing-weight context and body-composition estimation, not as a direct medication order.
Lean Body Mass LBM
Adult lean body mass and dosing-weight context calculator
Quick summary
Lean body mass (LBM) estimates body weight excluding most fat mass. It includes muscle, organs, bone, water, and other non-fat tissues. This adult calculator uses height, weight, sex, and the selected Boer or Hume formula to provide a body-composition estimate for dosing-weight context and CPB flow discussions.
Key info
Estimate lean body mass for dosing-weight context and actual vs lean BSA comparison.
Boer and Hume LBM formulas.
LBM is an estimate, not a standalone medication dose or clinical order.
Flow comparison table (CI 1.0 – 3.0)
BSA actual vs BSA lean flow comparison
| CI | Flow (Actual BSA) | Flow (Lean BSA) |
|---|
Practical note
Use lean-BSA flow as a comparison reference and interpret it with SvO₂, lactate, perfusion pressure, temperature, and local protocol.
Lean body mass methodology, FAQ & limitations
What is lean body mass?
Lean body mass estimates body weight excluding most fat mass. It includes muscle, organs, bone, water, and other non-fat tissues.
How is LBM calculated?
LBM is calculated from height, weight, sex, and the selected supported formula. This page supports Boer and Hume adult equations. Different formulas may produce different values, especially at very low or very high body weight.
Is lean body mass the same as ideal body weight?
No. Lean body mass and ideal body weight are different estimates. Ideal body weight is usually height-based, while lean body mass attempts to estimate non-fat body mass using height, weight, sex, and formula-specific assumptions.
Can this be used for medication dosing?
This calculator can support dosing-weight estimation, but it does not define a medication dose by itself. Drug dosing should follow the relevant drug label, institutional protocol, renal/hepatic function, indication, and clinical judgment.
What are the limitations of LBM formulas?
LBM formulas are population-based estimates and may be less accurate in children, pregnancy, edema, ascites, amputation, extreme obesity, cachexia, or unusual body composition. This calculator is intended for adult estimation; pediatric use is not validated here.
Extended clinical notes & evidence
Additional interpretation for obesity, lean-BSA flow comparison, and CPB context.
Actual BSA vs lean BSA interpretation
Actual BSA-based flow may trend higher in obesity because total body weight contributes to BSA.
Lean BSA-based flow may provide a comparison reference that is closer to fat-free body size.
Neither value should be used alone; bedside perfusion markers remain essential.
LBM formula notes
Adult LBM estimation formulas (Weight in kg, Height in cm).
Boer
Commonly used adult LBM estimation formula.
Equation
Male: LBM = 0.407 × weight + 0.267 × height − 19.2
Female: LBM = 0.252 × weight + 0.473 × height − 48.3
Hume
Alternative adult LBM estimation formula.
Equation
Male: LBM = 0.32810 × weight + 0.33929 × height − 29.5336
Female: LBM = 0.29569 × weight + 0.41813 × height − 43.2933
Both formulas are estimates and can differ by sex, height, and weight. LBM is not directly measured body composition, and results should not be used as a stand-alone medication dose or clinical order.
Pediatric use: limited interpretation
This calculator is intended for adult lean body mass estimation. Pediatric body composition changes with growth, and adult equations such as Boer and Hume are not pediatric reference models.
For children, pregnancy, edema, ascites, amputation, cachexia, extreme obesity, or unusual body composition, formula accuracy may be reduced. Follow institutional protocols and interpret results with temperature, DO₂/SvO₂, lactate, NIRS, pressure, urine output, renal/hepatic function, indication, and overall clinical context.
Clinical interpretation in CPB
- Use the flow comparison as a discussion aid, not an automatic target.
- Interpret with SvO₂, lactate, perfusion pressure, temperature, urine output, and local protocol.
- In obesity, actual BSA flow and lean BSA flow may diverge meaningfully.
- Consistency and clinical context are more important than a single calculated number.
Selected references
- Boer P. Estimated lean body mass as an index for normalization of body fluid volumes in humans. Am J Physiol. 1984.
- Hume R. Prediction of lean body mass from height and weight. J Clin Pathol. 1966.