Creatinine Clearance Calculator
Estimate kidney function for drug dose adjustment. Cockcroft-Gault formula with KDIGO CKD staging.
Mild decrease — usually no dose adjustment needed for most drugs.
Frequently asked questions
Cockcroft-Gault is still the formula used in nearly all drug-dose adjustment tables (FDA labels, Sanford Guide, Stockley's). eGFR formulas (MDRD, CKD-EPI) are used for CKD staging and screening but most drug labels still cite CrCl from Cockcroft-Gault. When using a drug label or dosing reference, use whatever formula it cites — usually Cockcroft-Gault.
Women have lower muscle mass on average, so they produce less creatinine. Without the correction, the formula would over-estimate kidney function in women. The 0.85 factor reflects the population-level difference. For trans patients on hormone therapy or non-binary patients, use clinical judgement — there's no consensus formula adjustment yet.
When BMI is >30 (obesity). Using actual body weight in obese patients over-estimates CrCl because adipose tissue doesn't contribute to creatinine production proportionally. Adjusted body weight (IBW + 0.4 × (actual - IBW)) gives a more accurate estimate. The tool flips to adjusted weight automatically if BMI > 30 and you've ticked the box.
For underweight (BMI <18.5), use actual body weight. For severe muscle wasting (cachexia, paralysis, amputation), Cockcroft-Gault may overestimate CrCl. Consider measured 24-hour urine collection or a cystatin C-based estimate if available.
Cockcroft-Gault has an inherent ±10-20% accuracy compared to gold-standard inulin clearance. Reporting 73.4 mL/min implies precision the formula doesn't have. Round to whole numbers; the KDIGO stage band matters more than the exact figure.
No. Cockcroft-Gault is validated only for adults ≥18. For paediatric patients (1-17 years), use the Schwartz formula or the modified Schwartz (uses serum creatinine + height). Most paediatric drug-dose adjustments are based on weight-based mg/kg dosing rather than CrCl staging.
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