Ideal body weight (Devine)

Calculate ideal body weight from height and sex using the Devine equations, with adjusted body weight and percentage of IBW alongside.

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What is this for?

Ideal body weight is a height-derived estimate of lean mass. It was devised for gentamicin dosing and remains the dosing weight for drugs that distribute poorly into adipose tissue. It is also the anchor for adjusted body weight and for the Cockcroft–Gault weight decision.

How to use it

Select the sex used by the dosing reference you are following.
Enter the height in centimetres or inches.
Optionally add the total body weight to obtain adjusted body weight and percentage of IBW in the same view.

Worked example

A 178 cm male weighs 110 kg. Calculate his ideal and adjusted body weights.

Answer: 178 cm = 70.1 in, which is 10.1 in over 5 feet. IBW = 50 + (2.3 × 10.1) = 73.2 kg. AdjBW = 73.2 + 0.4 × (110 − 73.2) = 87.9 kg.

Clinical pearls & pitfalls

IBW depends only on height and sex. Two patients of the same height have the same IBW regardless of what they weigh — that is the point of it.
If total body weight is below IBW, use total body weight. IBW is a ceiling for lean-mass-dosed drugs, not a floor.
The Devine equations were published for gentamicin dosing and were never validated as a measure of healthy or desirable weight. Do not present IBW to a patient as a weight target.
Work in total inches over 60, not in feet and inches. Converting 5 ft 10 in to "5 and 10" rather than 70 is a recurring arithmetic error.

Assumptions & limitations

Undefined below 152.4 cm (5 feet). PharmCalc blocks the calculation rather than returning an unvalidated extrapolation.
Derived in adults; not applicable to children.
Binary sex constants with no validated equation for intersex or transgender patients. Document which constant you used and why.
Devine is one of several IBW formulae (Robinson, Miller, Hamwi) that give different answers. Use the one your dosing reference assumed.

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.
Bauer LA. Applied Clinical Pharmacokinetics. 3rd ed. McGraw-Hill.