Adjusted Body Weight Calculator
Calculate adjusted body weight (AjBW) from height, actual weight, and a correction factor (0.25, 0.30, or 0.40) for clinical pharmacology and nutrition dosing.
Patient details
Adjusted body weight
190.7 lb
- Ideal body weight (Devine)
- 171.1 lb
- Actual weight
- 220 lb
- BMI
- 29.8
- Percent over IBW
- 28.6%
Typical clinical dosing: use adjusted body weight for this patient at this percent-over-IBW.
For information only. Not a substitute for clinical judgement or pharmacist review.
Frequently Asked Questions about the Adjusted Body Weight Calculator
What is adjusted body weight (AjBW)?
Adjusted body weight is a partial correction between ideal and actual body weight, used in clinical dosing when actual weight overestimates true lean mass. The formula is AjBW = IBW + correction times (actual minus IBW), with the correction factor commonly 0.4.
When should I use actual, ideal, or adjusted body weight for dosing?
Use actual when the drug distributes evenly across tissues (most water-soluble drugs in non-obese patients). Use ideal for drugs with poor adipose distribution. Use adjusted for drugs in obese patients where actual overshoots and ideal undershoots, like aminoglycosides.
Why are there three correction factors (0.25, 0.30, 0.40)?
Different drug classes and clinical settings use different factors based on published pharmacokinetic studies. 0.4 is the most common general default. 0.3 and 0.25 appear in specific contexts (some nutrition and aminoglycoside protocols). Follow your institution's guidance.
What is the Devine formula?
The Devine formula, published in 1974, estimates ideal body weight from height. Men: IBW kg equals 50 plus 2.3 times (height in inches minus 60). Women: 45.5 plus 2.3 times (height in inches minus 60). It is the most common IBW formula in US clinical settings.
Is this calculator a substitute for clinical judgement?
No. It is a math tool. Drug dosing decisions also depend on renal and hepatic function, drug-specific guidelines, age, comorbidities, and pharmacist review. Use the result alongside, not instead of, full clinical context.
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