⚖️ Adjusted Body Weight Calculator – Clinical Dosing & Nutrition Reference
The Adjusted Body Weight (AdjBW) calculator is a clinical tool used when a patient's actual body weight (ABW) substantially exceeds their ideal body weight (IBW). In obese or overweight adults, using raw ABW for medication dosing or energy calculations can overestimate requirements, while using IBW alone may underestimate them. AdjBW provides a practical middle ground by accounting for the partial contribution of excess adipose tissue.
The AdjBW Formula
The core formula is straightforward:
AdjBW = IBW + factor × (ABW − IBW)The default correction factor is 0.4, meaning 40% of the excess weight above ideal body weight is added to IBW. Some clinical protocols use alternative factors such as 0.25 or 0.5. This calculator lets you customize the factor for institution-specific workflows.
Ideal Body Weight (IBW) Formulas
IBW is calculated from height and sex using one of four validated regression equations:
- Devine (default): Male = 50 kg + 2.3 kg per inch over 5 ft; Female = 45.5 kg + 2.3 kg per inch over 5 ft
- Hamwi: Male = 48 kg + 2.7 kg per inch over 5 ft; Female = 45.5 kg + 2.2 kg per inch over 5 ft
- Robinson: Male = 52 kg + 1.9 kg per inch over 5 ft; Female = 49 kg + 1.7 kg per inch over 5 ft
- Miller: Male = 56.2 kg + 1.41 kg per inch over 5 ft; Female = 53.1 kg + 1.36 kg per inch over 5 ft
Enable Formula Comparison Mode to see how the choice of IBW equation affects the final AdjBW — useful for clinical review when multiple references use different formulas.
When Is Adjusted Body Weight Used?
AdjBW is commonly applied in the following clinical scenarios:
- Medication dosing — aminoglycosides, vancomycin, low-molecular-weight heparin, and other drugs where volume of distribution is affected by body composition
- Nutrition support — estimating caloric and protein targets in critically ill or obese patients using indirect calorimetry or predictive equations
- Creatinine clearance — the Cockcroft–Gault equation recommends AdjBW when actual weight exceeds ideal weight by more than 30%
- Ventilator tidal volume settings — IBW (or predicted body weight, which is nearly identical) is used to calculate lung-protective ventilation targets
IBW vs ABW vs AdjBW – Which Should You Use?
The choice of weight reference depends on the clinical context:
- Use IBW when dosing drugs with negligible distribution into adipose tissue, or for lung-protective ventilation settings.
- Use ABW when the patient's weight is at or below IBW, or for highly lipophilic drugs that distribute extensively into fat tissue.
- Use AdjBW when ABW exceeds IBW by 20–30% or more, for drugs or calculations where partial adipose distribution matters.
Unit Support
This calculator accepts height in cm, m, inches, orfeet + inches, and weight in kg or lb. All calculations are normalized to kilograms and inches internally, then displayed in your preferred units.