Adjusted Body Weight Calculator
Compute adjusted body weight (AjBW) from ideal and actual weight — the dosing weight used for many medications in overweight patients.
How it works
IBW (Devine): men 50 + 2.3×(in over 5 ft), women 45.5 + 2.3×(in over 5 ft) · AjBW = IBW + 0.4 × (actual − IBW)
Adjusted body weight bridges ideal and actual weight for patients who carry extra mass, because fat tissue holds some but not all drug and adds less to organ function than lean tissue. The standard correction factor of 0.4 adds 40% of the excess over ideal weight, and this AjBW is the dosing weight recommended for aminoglycosides and several other medicines in overweight adults. When actual weight is at or below ideal there is no excess to correct, so adjusted weight simply equals actual weight.
Worked example
A 175 cm man has a Devine ideal weight of 50 + 2.3 × 8.9 = 70.5 kg. At an actual 95 kg the excess is 24.5 kg, so AjBW = 70.5 + 0.4 × 24.5 = 80.3 kg.
Frequently asked questions
When is adjusted body weight used?
It is the recommended dosing weight for several drugs — notably aminoglycoside antibiotics — in patients whose actual weight is well above ideal, where using total weight would over-dose and ideal weight would under-dose.
Why 0.4 as the correction factor?
Roughly 40% of excess weight above ideal behaves like lean tissue for drug distribution. The 0.4 factor is a widely used clinical convention, though some protocols use other values.
What if my weight is below ideal?
Then there is no excess to adjust, and adjusted body weight equals your actual weight — dosing uses the real number.
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Educational estimate using standard formulas and population averages — not medical advice. Talk to a qualified clinician before making decisions about diet, training, or pregnancy.