What is lean body weight and how is it different from lean body mass?

Lean body weight (LBW) and lean body mass (LBM) are often used interchangeably. Both refer to total body weight minus fat mass — essentially everything that is not fat: muscle, bone, water, and organs. In clinical drug dosing, LBW is the preferred scalar for certain high-lipophilicity drugs because it avoids over-dosing in obese patients while still scaling for larger lean tissue volumes.

Which formula should I use — Janmahasatian or Hume?

The Janmahasatian (2005) formula is recommended for most clinical applications. It was derived from a larger, more diverse sample and uses BMI as a correction factor, which makes it more accurate across a wide range of body sizes including obese patients. The Hume (1966) formula is shown for historical comparison and tends to overestimate LBW in obese patients.

Which drugs use lean body weight for dosing?

Drugs where LBW is the primary dosing scalar include propofol (induction), succinylcholine, rocuronium, vecuronium, and some aminoglycosides. Always verify against current institutional guidelines or pharmacist recommendations — dosing practices vary by protocol.

Is this calculator suitable for pediatric patients?

The Janmahasatian formula was validated in adults. It should not be applied to children or adolescents. Pediatric drug dosing uses separate weight-based or body surface area formulas.

Why might LBW exceed total body weight in very lean individuals?

Both formulas include biological constants calibrated for average body compositions. In very lean or muscular individuals with a low BMI, the formula can theoretically approach or exceed actual weight. In practice, LBW is capped at total body weight, since lean mass cannot exceed total mass.

Lean Body Weight Calculator

Name: Lean Body Weight Calculator
Availability: InStock
Author: Nham Vu

Enter your weight, height, and sex to calculate Lean Body Weight using the Janmahasatian (2005) and Hume formulas, with BMI and estimated body fat.

Enter Your Measurements

Unit System

Weight (kg)

Height (cm)

Sex

Male Female

Enter your measurements and click Calculate.

Summary

Enter your weight, height, and sex to calculate Lean Body Weight using the Janmahasatian (2005) and Hume formulas, with BMI and estimated body fat.

How it works

Select your unit system — Metric (kg/cm) or Imperial (lbs/ft+in).
Enter your body weight.
Enter your height.
Select your sex (Male or Female).
Click Calculate — LBW, BMI, and body fat estimate appear instantly from both formulas.
Click Reset to clear all fields.

Use cases

Calculate propofol induction dose using lean body weight in obese patients.
Determine dosing weight for neuromuscular blocking agents (rocuronium, vecuronium).
Compare Janmahasatian and Hume LBW values before pharmacokinetic calculations.
Estimate lean body mass alongside BMI in a clinical or research setting.

Frequently Asked Questions

Last updated: 2026-07-23 · Reviewed by Nham Vu