Adjusted Body Weight Calculator

In clinical settings, simply using a patient's physical weight on a scale (Actual Body Weight) is incredibly dangerous when dosing certain powerful medications, especially hydrophilic (water-loving) drugs like Aminoglycoside antibiotics. Because these drugs cannot easily penetrate fatty tissue (adipose), giving an obese patient a dosage based on their total weight will result in a toxic concentration of the drug in their lean muscle and blood.

Part 1: The Devine Formula (IBW)

Before finding the Adjusted weight, we must find the Ideal Body Weight (IBW). Introduced in 1974, the Devine formula is the global medical standard:

Part 2: The 120% Threshold Check

You do not use Adjusted Body Weight for everyone. You only use it if the patient is considered clinically obese against their IBW benchmark.

• If Actual Weight is under 120% of IBW: Use Actual or IBW (follow standard drug guidelines).
• If Actual Weight is over 120% of IBW: Safe to proceed with Adjusted Body Weight calculate below.

Part 3: The Adjusted Body Weight Formula

Because roughly 40% of excess fat weight *does* require some drug distribution, pharmacists use a 0.4 correction multiplier: