Adjusted Body Weight Calculator
Enter height, sex, and actual body weight to get IBW (Devine formula), percent over IBW, and AdjBW when actual weight exceeds 130% of IBW.
Adjusted body weight (AdjBW) = IBW + 0.4 × (actual weight − IBW), where IBW is ideal body weight from the Devine formula.
Use the Adjusted Body Weight Calculator
Patient Parameters
Clinical use note: AdjBW is commonly recommended for aminoglycosides (gentamicin, tobramycin, amikacin) when actual weight exceeds 130% of IBW. Note that vancomycin consensus guidelines recommend using actual body weight (ABW) for initial dosing, not AdjBW.
Educational reference only. All dosing decisions must be verified by a licensed pharmacist or physician. This tool does not replace clinical judgment.
Enter patient data and click Calculate
Ideal Body Weight (Devine Formula)
Obesity Assessment
Adjusted Body Weight (AdjBW)
AdjBW = IBW + 0.4 × (ABW − IBW)
Quick answer
Adjusted body weight (AdjBW) = IBW + 0.4 × (actual weight − IBW), where IBW is ideal body weight from the Devine formula. It is used when actual weight is more than 130% of IBW; below that, actual weight is used.
Examples
| Patient | IBW | 130% of IBW | AdjBW |
|---|---|---|---|
| Male, 5 ft 10 in, 120 kg | 73.0 kg | 94.9 kg | 91.8 kg |
| Female, 5 ft 4 in, 100 kg | 54.7 kg | 71.1 kg | 72.8 kg |
| Female, 5 ft 6 in, 85 kg | 59.3 kg | 77.1 kg | 69.6 kg |
| Male, 6 ft 0 in, 90 kg | 77.6 kg | 100.9 kg | Not used (under 130%) |
Enter height, sex and weight.
Summary
This tool calculates Ideal Body Weight (IBW) using the Devine formula, determines whether the patient is obese (actual weight > 130% of IBW), and computes Adjusted Body Weight (AdjBW = IBW + 0.4 × (ABW − IBW)) when applicable. AdjBW is commonly used as the dosing weight for aminoglycosides (gentamicin, tobramycin, amikacin) in obese patients; in contrast, vancomycin empiric dosing in obesity generally uses actual body weight per consensus guidelines. Height can be entered in centimeters or feet and inches; body weight in kilograms or pounds. Results include IBW, percent over IBW, applicability of AdjBW, and AdjBW in both kg and lbs. All results are for educational reference — verify with a licensed pharmacist or physician before clinical use.
How it works
- Enter the patient's height (cm or ft/in) and select biological sex.
- Enter the patient's actual body weight (kg or lbs).
- IBW is calculated using the Devine formula: 50 kg (male) or 45.5 kg (female) + 2.3 kg per inch over 5 ft.
- Percent over IBW is computed as (ABW − IBW) / IBW × 100.
- If actual weight exceeds 130% of IBW, AdjBW is applicable and computed as IBW + 0.4 × (ABW − IBW).
- Results display IBW, percent over IBW, AdjBW applicability, and AdjBW in kg and lbs.
Use cases
- Determine the appropriate dosing weight for aminoglycosides in an obese patient.
- Evaluate whether to use IBW, ABW, or AdjBW for aminoglycoside dosing.
- Quickly assess whether a patient meets the obesity threshold for AdjBW dosing.
- Convert between IBW and AdjBW for pharmacy students learning clinical pharmacokinetics.
- Support clinical pharmacists performing medication reviews for obese inpatients.
- Cross-check a manually calculated AdjBW during ward rounds.