Adjusted Body Weight Calculator

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.

There is no universal choice. The correct weight scalar depends on the medication, indication, renal function, patient population, and local protocol. Actual, ideal, lean, and adjusted body weight can produce materially different doses. Use this calculator only after the drug-specific guidance or a clinical pharmacist has identified the required formula and correction factor.

Correction factors come from drug-specific pharmacokinetic studies and local protocols. A factor of 0.40 is common in some aminoglycoside protocols, but it is not a general dosing default. Values of 0.25 or 0.30 may appear in other protocols. Select a factor only when the applicable prescribing information, institutional policy, or clinical pharmacist specifies it.

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.

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.