Health
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 clinically derived weight used when actual weight would overestimate a drug's distribution into lean tissue. The formula is AjBW = IBW + correction factor x (actual weight - IBW), where the default correction factor is 0.40. It applies only when actual weight exceeds ideal body weight; if you are at or under your IBW, the calculator returns your actual weight unchanged.
When should I use actual, ideal, or adjusted body weight for dosing?
Use actual weight for most water-soluble drugs in non-obese patients, where weight and lean mass track closely. Use ideal body weight (IBW) for drugs with poor adipose distribution. Use adjusted body weight for obese patients when actual weight overshoots and IBW undershoots, most commonly with aminoglycosides. This calculator also flags when actual weight exceeds IBW by less than 20%, because in that range actual weight alone is often adequate.
Why are there three correction factors (0.25, 0.30, 0.40)?
Each factor comes from pharmacokinetic studies for a specific drug class or clinical protocol. The 0.40 default covers general use and aminoglycosides in most published guidelines. Factors of 0.30 and 0.25 appear in certain nutrition support and niche antibiotic protocols. Your institution's formulary or a clinical pharmacist should confirm which applies to your drug and patient.
What is the Devine formula?
The Devine formula (1974) estimates IBW from height. For men: IBW (kg) = 50 + 2.3 x (height in inches - 60). For women: IBW (kg) = 45.5 + 2.3 x (height in inches - 60). It is the standard IBW formula in US clinical practice. The formula was developed for adults 60 inches (5 ft) or taller; results for shorter heights are less reliable and this calculator displays a warning below that threshold.
Is this calculator a substitute for clinical judgment?
No. It performs the math; the clinical decision is yours. Drug dosing also depends on renal and hepatic function, age, comorbidities, drug-specific guidelines, and pharmacist review. Treat the output as a reference point, not a prescription.