What Is an Adjusted Body Weight Dosing Calculator?
Adjusted body weight (ABW) is a dosing weight used for certain medications in patients whose actual body weight is well above their ideal body weight. Dosing purely on actual weight can over-dose obese patients for drugs that don't distribute proportionally into fat tissue, while dosing purely on ideal weight can under-dose them. ABW splits the difference using a standard correction factor.
This calculator first computes ideal body weight (IBW) using the widely used Devine formula, then applies the adjusted body weight formula when actual weight exceeds that ideal.
How to Read Your Results
Adjusted Body Weight
The dosing weight to use for medications whose guidelines specify adjusted body weight (commonly aminoglycoside antibiotics, among others). If actual weight doesn't exceed IBW, this equals actual weight.
Ideal Body Weight (Devine)
Calculated from height and sex using the Devine formula, this represents a population-average "ideal" weight for that height, independent of the patient's actual weight.
Actual Body Weight
Your entered weight, converted to kilograms for the calculation, shown for reference.
Adjustment Applied
Tells you whether the adjustment formula was actually used (only relevant when actual weight is above ideal body weight).
Real-World Example
A male patient is 70 inches (5'10") tall and weighs 100 kg.
| Metric | Value |
|---|---|
| Height | 70 in |
| Actual weight | 100 kg |
| Ideal body weight (Devine) | 73.0 kg |
| Adjusted body weight | 83.8 kg |
Since the actual weight (100 kg) is well above the ideal (73.0 kg), the adjustment applies: 73.0 + 0.4 × (100 − 73.0) = 83.8 kg — the dosing weight to use for drugs whose guidance calls for adjusted body weight.
Tips for Using This Calculator
- Not every drug uses adjusted body weight. Check the specific medication's dosing reference — some use actual weight, some ideal, some adjusted, and some a capped weight.
- The Devine formula was derived for adults and is generally applied to patients over about 5 feet tall; results below that height are less reliable.
- Adjusted body weight is typically only calculated when actual weight exceeds ideal body weight (i.e., in overweight or obese patients).
- Always double-check dosing weight decisions against current institutional protocols or a pharmacist.
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Last updated: August 2026 · Reviewed by: Simple Calculator Tools Editorial Team