Adjusted Body Weight (AdjBW) Calculator
Calculate adjusted body weight for obese patients when protocols call for IBW + fraction of excess weight.
Understanding this tool
Why nurses use it
For obese patients, some drug protocols dose using adjusted body weight (IBW plus a fraction of excess weight) rather than full actual weight — common in aminoglycosides and some anaesthetic references.
When to use it
Use only when the specific drug protocol calls for adjusted body weight — confirm factor (often 0.4) with pharmacy.
Calculate
How to use this calculator
- Enter height, sex, and actual weight.
- Review IBW and calculated AdjBW.
- Apply only per prescriber/pharmacy guidance.
How the calculation works
AdjBW = IBW + 0.4 × (actual weight − IBW). The 0.4 factor is common but not universal.
Formula used by this tool — verify units before applying at the bedside.
Worked example
Limitations & clinical notes
- 0.4 factor is common but not universal — follow pharmacy/prescriber guidance.
- Some drugs use IBW, actual weight, or different adjustment factors.
- AdjBW applies when actual weight exceeds IBW — not indicated when actual ≤ IBW.
References
Key sources: Obesity dosing in critical care literature.
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Disclaimer: This calculator is for educational and bedside double-check purposes only. It does not replace institutional protocols, prescriber orders, pharmacist verification, or clinical judgment. Always follow your local policies — especially for high-risk medications, infusions, pediatrics, and critical care. If the patient is acutely unwell, escalate immediately rather than relying on any calculator output.