Ideal body weight calculator (Devine) and adjusted body weight
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Result
For exam practice only. This is a study aid, never a clinical decision: always follow the prescription, local protocols and the product information.
Calculate the ideal body weight (IBW) with the Devine formula, the one most often used in drug dosing and ventilator settings, and compare it with the Robinson, Miller and Hamwi formulas. Add the actual weight to get the percentage of ideal weight and the adjusted body weight that some dosing rules use for obese patients.
Step-by-step solution
Height in inches above 5 feet
Ideal body weight (Devine)
Other formulas
Compared with the actual weight
Key formulas
- Ideal body weight (Devine)
- men 50 + 2.3 × (in − 60); women 45.5 + 2.3 × (in − 60); 1 in = 2.54 cm
How to calculate ideal body weight
- Convert the height to inches (cm ÷ 2.54) and subtract 60 inches (5 feet).
- Devine: IBW = 50 kg + 2.3 kg per inch above 5 feet for men, 45.5 kg + 2.3 kg per inch for women.
- For a man of 175 cm: 175 ÷ 2.54 = 68.9 in, 8.9 in above 5 feet, IBW = 50 + 2.3 × 8.9 = 70.5 kg.
- Adjusted body weight = IBW + 0.4 × (actual weight − IBW), used when the actual weight is well above the IBW.
Questions and answers
Where does the Devine formula come from?
From B. J. Devine (Drug Intelligence and Clinical Pharmacy, 1974), who proposed it for dosing gentamicin. Hamwi (1964), Robinson (1983) and Miller (1983) published alternatives; all start at 5 feet.
What about people shorter than 5 feet?
The formulas are not defined below 152.4 cm. Some references subtract 2.3 kg per inch below 5 feet, but the result is unreliable; the calculator warns about it.
When is the adjusted body weight used?
For some drugs in obese patients, often when the actual weight is more than about 120% of the IBW. The factor 0.4 is the most common; follow the protocol for the drug.
Which weight is used for ventilator tidal volumes?
The predicted body weight, which uses the same Devine-style formula (50 or 45.5 kg + 2.3 kg per inch above 5 feet).
Practise it yourself
Practise Enteral & parenteral nutrition calculations
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