Creatinine Clearance Calculator (Cockcroft-Gault)
Calculate creatinine clearance using the Cockcroft-Gault equation.
Estimates kidney function for medication dosing.
Supports metric and imperial units.
Creatinine clearance (CrCl) estimates the glomerular filtration rate (GFR) — the rate at which the kidneys filter blood — using serum creatinine levels, age, weight, and sex. It is the primary clinical measure of kidney function and directly affects drug dosing for renally-cleared medications.
Cockcroft-Gault formula (most widely used clinically): CrCl (mL/min) = [(140 − Age) × Weight (kg)] / [72 × Serum Creatinine (mg/dL)] × 0.85 for females (women have lower muscle mass and thus lower creatinine production)
Kidney function stages by GFR/CrCl:
| Stage | GFR (mL/min) | Description |
|---|---|---|
| G1 (Normal) | ≥ 90 | Normal or high |
| G2 (Mildly decreased) | 60–89 | Mildly decreased |
| G3a | 45–59 | Mildly to moderately decreased |
| G3b | 30–44 | Moderately to severely decreased |
| G4 (Severely decreased) | 15–29 | Severely decreased |
| G5 (Kidney failure) | < 15 | Dialysis or transplant |
Alternative: MDRD equation (for research and eGFR reporting): eGFR = 175 × Serum Creatinine^(−1.154) × Age^(−0.203) × 0.742 (if female) × 1.212 (if Black)
Drug dosing implications: Renal clearance affects: antibiotics (vancomycin, aminoglycosides), anticoagulants (enoxaparin), antivirals (acyclovir, tenofovir), and many cardiac drugs. Nephrotoxic drugs require CrCl monitoring every 48–72 hours in critical care.
Worked example: Patient: 68-year-old male, weight 80 kg, serum creatinine 1.4 mg/dL. CrCl = [(140 − 68) × 80] / [72 × 1.4] = [72 × 80] / [100.8] = 5,760 / 100.8 = 57.1 mL/min → Stage G3a (mildly to moderately decreased kidney function)
A vancomycin dose that would be appropriate for normal kidneys would require significant reduction at this CrCl to prevent drug accumulation and nephrotoxicity.
Important: Creatinine-based estimates are less reliable in elderly, malnourished, or obese patients. Cystatin C-based eGFR is preferred in these populations.