The ideal body weight calculator uses the Devine formula to estimate a patient's IBW based on height and sex. IBW is used instead of actual body weight for drug dosing in many clinical situations — particularly aminoglycoside antibiotics (gentamicin, tobramycin), initial ventilator tidal volume settings, and nutritional calculations. When a patient's actual weight exceeds 130% of their IBW, Adjusted Body Weight (ABW) is calculated to account for the increased drug distribution in obese patients.
Use IBW for: initial ventilator tidal volume settings, aminoglycoside dosing (gentamicin, tobramycin), most general drug dosing references.
Use ABW for: patients who are obese (actual weight more than 130% of IBW), some chemotherapy regimens, and weight-based heparin in obese patients.
Use Actual Body Weight for: patients at or below their IBW, hydrophilic drugs, and paediatric dosing.
Use IBW for aminoglycosides, initial ventilator tidal volumes, and as a starting point for nutritional calculations. Use Adjusted Body Weight (ABW) when the patient is obese (actual weight >130% of IBW). Use actual body weight when the patient weighs less than their IBW.
For males: IBW (kg) = 50 + 2.3 × (height in inches − 60). For females: IBW (kg) = 45.5 + 2.3 × (height in inches − 60). The formula requires height above 5 feet (60 inches / 152 cm) to be valid.