Ideal Body Weight (Devine) Calculator
The Devine formula for ideal body weight (IBW) was published in 1974 and remains the standard reference for drug dosing and mechanical ventilator settings. It estimates the healthy weight for a given height and sex. Males: IBW = 50 kg + 2.3 kg for each inch of height above 60 inches (5 feet). Females: IBW = 45.5 kg + 2.3 kg for each inch above 60 inches. IBW is particularly important in pharmacokinetics for drugs with narrow therapeutic windows, and in critical care for setting lung-protective tidal volumes. Enter height in inches (or convert from feet and inches) and select biological sex to calculate IBW in kilograms. This tool is for educational and reference purposes only.
Devine formula
Male IBW (kg) = 50 + 2.3 x (height in inches - 60)
Female IBW (kg) = 45.5 + 2.3 x (height in inches - 60)
Height is in inches. For heights at or below 60 inches (5 feet), the formula returns the base value (50 kg male, 45.5 kg female). Convert feet and inches to total inches: total inches = (feet x 12) + inches.
Clinical applications of IBW
- Drug dosing: Aminoglycosides, some chemotherapy agents, and other renally/weight-adjusted drugs use IBW or ABW to prevent toxicity in obese patients.
- Mechanical ventilation: Tidal volume of 6-8 mL/kg predicted body weight (IBW-based) per ARDSNet lung-protective strategy.
- Nutrition: Some enteral/parenteral nutrition protocols reference IBW for protein and calorie targets.
- Adjusted body weight (ABW): IBW + 0.4 x (actual weight - IBW). Used for obese patients when actual weight would over-dose and IBW would under-dose.
Frequently asked questions
What is the Devine formula for ideal body weight?
The Devine formula calculates IBW as: Male: 50 kg + 2.3 kg per inch above 60 inches (5 feet). Female: 45.5 kg + 2.3 kg per inch above 60 inches. For heights at or below 60 inches, IBW equals the base value (50 or 45.5 kg). Height is measured in inches.
What is ideal body weight used for?
IBW is used to calculate drug doses for medications where actual body weight may lead to toxicity in obese patients, including aminoglycosides, vancomycin (for some protocols), and analgosedation in the ICU. IBW is also used to set tidal volume targets in mechanical ventilation (predicted body weight, which uses IBW-based formulas).
How does IBW differ from actual and adjusted body weight?
IBW is an estimated healthy weight for height. Actual body weight is what the patient weighs. Adjusted body weight (ABW = IBW + 0.4 x (actual - IBW)) is used for obese patients when neither IBW alone nor actual body weight is appropriate for dosing.
What is predicted body weight for mechanical ventilation?
Predicted body weight (PBW) uses a similar but slightly different formula: Male: 50 + 2.3 x (height in inches - 60). Female: 45.5 + 2.3 x (height in inches - 60). This is essentially the Devine IBW and is used to set tidal volumes of 6-8 mL/kg PBW in lung-protective ventilation per ARDSNet protocols.
Are there alternative IBW formulas?
Yes. The Robinson formula (1983), Miller formula (1983), and Hamwi method are alternatives. Devine's formula is the most widely used in clinical practice and pharmacokinetic studies. For very short patients, the formula can yield unrealistically low values; clinical judgment should be applied.
Official sources
- NIH National Library of Medicine: PubMed (Devine BJ 1974, original publication).
- NIH NHLBI ARDSNet Protocol: ARDS Information and Ventilator Management.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.