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Creatinine Clearance Calculator with Ideal Body Weight (Obesity)
In obese patients, using actual body weight in the Cockcroft-Gault equation overestimates creatinine clearance, so ideal body weight (IBW) or adjusted body weight is generally preferred for renal drug dosing. This calculator lets you switch the weight basis: Devine IBW is 50 kg (male) or 45.5 kg (female) plus 2.3 kg per inch over 60 inches, and adjusted body weight is IBW + 0.4 × (actual − IBW). For example, a 6-foot (72-inch) man has a Devine IBW of about 77.6 kg regardless of his actual weight. The tool then applies Cockcroft-Gault to whichever weight basis you choose and shows the resulting CrCl with its general renal-dosing tier. One important caveat: the weight basis is drug-specific — some agents such as vancomycin and aminoglycosides are dosed on actual body weight per protocol, so do not blanket-apply IBW. This is an estimate for dose adjustment, not dosing advice, and a clinician decision. Free, private, and computed entirely in your browser.
Devine IBW = 50 ♂ / 45.5 ♀ + 2.3 kg per inch over 60 in
- Adjusted body weight = IBW + 0.4 × (actual − IBW)
- In obesity, actual weight overestimates CrCl — use IBW or adjusted
Frequently asked questions
Should I use ideal body weight for creatinine clearance in obese patients?
Generally yes for the CrCl estimate — actual body weight overestimates creatinine clearance in obesity, so ideal body weight (Devine) or adjusted body weight is preferred. Adjusted body weight = IBW + 0.4 × (actual − IBW). But the weight basis is drug-specific: some drugs (e.g. vancomycin, aminoglycosides) are dosed on actual weight per protocol, so check the individual drug.
How is ideal body weight calculated?
The Devine formula gives ideal body weight as 50 kg for men or 45.5 kg for women, plus 2.3 kg for each inch of height over 60 inches. A 70-inch man is 50 + 2.3 × 10 = 73 kg; a 69-inch man is 50 + 2.3 × 9 = 70.7 kg. This calculator computes it from the height you enter and can apply it (or adjusted body weight) in the Cockcroft-Gault estimate.