Adjusted Body Weight Calculator

Enter height, sex, and actual body weight to get IBW (Devine formula), percent over IBW, and AdjBW when actual weight exceeds 130% of IBW.

Use the Adjusted Body Weight Calculator

Patient Parameters

Clinical use note: AdjBW is commonly recommended for aminoglycosides (gentamicin, tobramycin, amikacin) when actual weight exceeds 130% of IBW. Note that vancomycin consensus guidelines recommend using actual body weight (ABW) for initial dosing, not AdjBW.

Educational reference only. All dosing decisions must be verified by a licensed pharmacist or physician. This tool does not replace clinical judgment.

Enter patient data and click Calculate

Summary

Enter height, sex, and actual body weight to get IBW (Devine formula), percent over IBW, and AdjBW when actual weight exceeds 130% of IBW.

How it works

  1. Enter the patient's height (cm or ft/in) and select biological sex.
  2. Enter the patient's actual body weight (kg or lbs).
  3. IBW is calculated using the Devine formula: 50 kg (male) or 45.5 kg (female) + 2.3 kg per inch over 5 ft.
  4. Percent over IBW is computed as (ABW − IBW) / IBW × 100.
  5. If actual weight exceeds 130% of IBW, AdjBW is applicable and computed as IBW + 0.4 × (ABW − IBW).
  6. Results display IBW, percent over IBW, AdjBW applicability, and AdjBW in kg and lbs.

Use cases

  • Determine the appropriate dosing weight for aminoglycosides in an obese patient.
  • Evaluate whether to use IBW, ABW, or AdjBW for aminoglycoside dosing.
  • Quickly assess whether a patient meets the obesity threshold for AdjBW dosing.
  • Convert between IBW and AdjBW for pharmacy students learning clinical pharmacokinetics.
  • Support clinical pharmacists performing medication reviews for obese inpatients.
  • Cross-check a manually calculated AdjBW during ward rounds.

Frequently Asked Questions

Last updated: 2026-09-19 · Reviewed by Nham Vu