Adjusted Body Weight

What This Calculator Measures

Provides a dosing weight for overweight and obese adults by combining ideal body weight with a fraction of the excess weight, used when medications require a body-weight-adjusted dose.

How to Use

1. Confirm the patient is overweight or obese, as this adjustment is intended for that population.
2. Select sex, and enter height and actual weight.
3. Review the adjusted body weight in kg.
4. Use the adjusted weight in place of actual weight only where drug-specific guidance calls for it.

Interpretation Guide

Adjusted body weight falls between ideal and actual body weight. It is intended for medication dosing in overweight and obese adults, where actual weight may lead to over-dosing and ideal weight to under-dosing.

Clinical Significance

Adjusted body weight helps balance the risk of over-dosing (with actual weight) and under-dosing (with ideal weight) for weight-based medications in obesity, where both extremes carry clinical risk.

When to Use

• Medication dosing in overweight and obese adults where the drug label or guidance specifies adjusted weight
• As a size-adjusted dosing weight when actual weight overestimates the relevant lean mass

When Not to Use

• In normal-weight patients, where the adjustment provides no benefit
• For all medications — many drugs are dosed by actual weight
• In children, where pediatric weight references apply
• Without checking drug-specific dosing guidance

Limitations

• The 0.4 adjustment factor is empirical and varies by source.
• Applies to adults; pediatric use requires other references.
• Is not a measure of body composition or lean mass.
• Whether to use actual, ideal, or adjusted weight depends on the specific drug.

Worked Example

A 45-year-old man who is 180 cm tall weighs 110 kg.

AdjBW = 75.0 + 0.4 × (110 − 75.0) = 89.0 kg, the adjusted dosing weight for this patient.

Evidence

Source

Internal Medicine / Pharmacy

Reference

ClinCalc Drug Dosing Reference. Adjusted Body Weight.

Reviewed By

MedCalcHub Clinical Team

Version

1.0

Updated

2026-08

1. ClinCalc Drug Dosing Reference. Adjusted Body Weight.
2. ASHP Clinical Guidelines on medication dosing in obese patients.

References

1. ClinCalc Drug Dosing Reference. Adjusted Body Weight. (Reference)
2. ASHP Clinical Guidelines on medication dosing in obese patients. (Guideline)