Cockcroft-Gault GFR Calculator
Medical Disclaimer: This tool is intended for informational and educational purposes only. It does not constitute medical advice or diagnosis. Always consult with a qualified healthcare professional for interpretation of kidney function tests.
About the Cockcroft-Gault Equation
The Cockcroft-Gault formula is a mathematical method used to estimate creatinine clearance (CrCl), which serves as a proxy for the Glomerular Filtration Rate (GFR). Developed in 1976, it remains one of the most widely used formulas in pharmacokinetics for adjusting drug dosages based on kidney function.
The Formula
The calculation considers age, body weight, serum creatinine levels, and biological sex. The base formula (for males) is:
CrCl = [(140 – Age) × Weight (kg)] / (72 × Serum Creatinine (mg/dL))
For females, the result is multiplied by 0.85 because women generally have lower muscle mass (and thus lower creatinine generation) than men of the same weight and age.
Interpreting Creatinine Clearance
Creatinine clearance is measured in milliliters per minute (mL/min). Lower values indicate reduced kidney function. While the MDRD and CKD-EPI equations are often preferred for staging Chronic Kidney Disease (CKD), Cockcroft-Gault is specifically preferred for drug dosing adjustments (e.g., antibiotics, anticoagulants).
| CKD Stage | Description | GFR Range (mL/min) |
|---|---|---|
| Stage 1 | Normal kidney function with other signs of damage | 90+ |
| Stage 2 | Mild loss of kidney function | 60 – 89 |
| Stage 3a | Mild to moderate loss | 45 – 59 |
| Stage 3b | Moderate to severe loss | 30 – 44 |
| Stage 4 | Severe loss of kidney function | 15 – 29 |
| Stage 5 | Kidney failure | Less than 15 |
Example Calculation
Consider a 60-year-old male weighing 75 kg with a serum creatinine of 1.2 mg/dL:
- Numerator: (140 – 60) × 75 = 80 × 75 = 6000
- Denominator: 72 × 1.2 = 86.4
- Result: 6000 / 86.4 = 69.4 mL/min
If this patient were female, the result would be 69.4 × 0.85 = 59.0 mL/min.