Ideal Body Weight Calculator — Free Online Calculator
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Optional: enter actual weight to calculate Adjusted Body Weight
Ideal Body Weight
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About This Calculator
Ideal Body Weight (IBW) estimates a person's weight based on height and sex using the Devine formula. IBW is commonly used in clinical practice for drug dosing (e.g., tidal volume calculations, aminoglycoside dosing) and nutritional assessment. Adjusted Body Weight (ABW) is used when actual weight significantly exceeds IBW, providing a more appropriate value for dosing calculations.
Formula
Interpretation
IBW is used as a reference point for clinical dosing. Patients significantly above or below IBW may require dose adjustments.
If actual weight exceeds IBW by more than 30%, Adjusted Body Weight is often recommended for drug dosing.
References
- Devine BJ. Gentamicin therapy. Drug Intell Clin Pharm. 1974;8:650-655.
- Pai MP, Paloucek FP. The origin of the "ideal" body weight equations. Ann Pharmacother. 2000;34(9):1066-1069.
Frequently Asked Questions
What is the Devine formula for ideal body weight?
For males: IBW (kg) = 50 + 2.3 × (height in inches − 60). For females: IBW (kg) = 45.5 + 2.3 × (height in inches − 60). This formula is based on height and was originally derived for drug dosing purposes.
When should I use adjusted body weight instead of IBW?
Adjusted body weight (AdjBW) is used for obese patients (actual weight >120% of IBW). AdjBW = IBW + 0.4 × (Actual Weight − IBW). This is important for drug dosing (e.g., aminoglycosides, vancomycin) and nutritional calculations.
Why is IBW important for ventilator settings?
Tidal volume in lung-protective ventilation is based on IBW (6–8 mL/kg IBW), not actual body weight. Using actual weight in obese patients can lead to injuriously high tidal volumes and ventilator-induced lung injury.
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⚠ Medical Disclaimer
This tool is for educational and informational purposes only. It is not intended to replace professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional for clinical decisions.