BMI & body weight calculator
BMI · IBW (Devine) · Adjusted BW · Lean BW — for weight-based dosing.
Formulas used
BMI
weight (kg) / height² (m²)IBW male (Devine)
50 + 2.3 × (height_in − 60)IBW female (Devine)
45.5 + 2.3 × (height_in − 60)AdjBW
IBW + 0.4 × (ABW − IBW)LBW male
(9270 × ABW) / (6680 + 216 × BMI)LBW female
(9270 × ABW) / (8780 + 244 × BMI)Sources: Janmahasatian LBW (2005) · Devine IBW (NCBI) · WHO BMI classification
Frequently asked questions
What is ideal body weight (IBW) and why does it matter for dosing?
IBW estimates the weight at a given height corresponding to a "normal" BMI. Many drugs — aminoglycosides, vancomycin, some chemotherapy — are dosed on IBW to avoid toxicity in obese patients. The Devine equation is the most widely used IBW formula. See also DailyMed labels for the weight basis specified per drug.
When should adjusted body weight (AdjBW) be used?
AdjBW is used when actual weight > IBW by ≥20%. Formula: AdjBW = IBW + 0.4 × (ABW − IBW). The correction factor 0.4 is drug-class dependent; some sources use 0.3 for certain agents. Reference: PMC dosing in obesity review and ASHP clinical resources.
What BMI thresholds does the WHO use?
WHO BMI thresholds: Underweight <18.5 · Normal 18.5–24.9 · Overweight 25–29.9 · Obesity I 30–34.9 · Obesity II 35–39.9 · Obesity III ≥40. Source: WHO obesity fact sheet.
What is lean body weight (LBW)?
LBW = total weight minus fat mass, estimated by Janmahasatian's equation: LBW(male) = (9.27×10³ × ABW) / (6.68×10³ + 216 × BMI) and analogous for female. Used for some anaesthetic agents and drugs with tissue-dependent distribution. Reference: Janmahasatian et al. (2005) Clin Pharmacokinet.