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Lean Body Weight (Janmahasatian)

Janmahasatian lean body weight (fat-free mass): men 9270 × W ÷ (6680 + 216 × BMI); women 9270 × W ÷ (8780 + 244 × BMI). Valid across extremes of body size and used for scaling drug doses in obesity.

  • Weight (kg or lb)
  • Height (cm or m or in)
  • Sex: Male; Female
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Formula

Men: LBW = 9270 × W ÷ (6680 + 216 × BMI). Women: LBW = 9270 × W ÷ (8780 + 244 × BMI). W in kg, BMI in kg/m².

Clinical pearls

  • Derived against DXA fat-free mass in adults with BMI 17–70; preferred over the older James formula, which becomes paradoxical at high BMI.
  • Used for dosing drugs that distribute mainly into lean tissue (e.g. some anesthetic induction agents).

Examples

lean body weight 100 kg 180 cm malelbw for a 70 kg 160 cm womanfat free mass 250 lbs 5'10" man

FAQ

What is the difference between lean body weight and ideal body weight?

Lean body weight estimates actual fat-free mass from weight and height; ideal body weight depends only on height and sex.

Evidence

  1. Janmahasatian S et al. Quantification of lean bodyweight. Clin Pharmacokinet 2005;44:1051–65.

General & Anthropometrics · Reviewed 2026-10-14 · Methodology