The creatinine clearance calculator estimates renal function using the Cockcroft-Gault equation, the most widely used formula for calculating CrCl in clinical pharmacology and drug dosing. CrCl is used to identify patients requiring drug dose adjustments due to reduced kidney function — particularly for aminoglycoside antibiotics, digoxin, renally-cleared anticoagulants, and many other medications. A CrCl of ≥90 mL/min indicates normal renal function; below 30 mL/min signals significant impairment requiring substantial dose adjustment.
| CrCl (mL/min) | Renal Function | Dosing implication |
|---|---|---|
| ≥ 90 | Normal | Standard dosing |
| 60–89 | Mild impairment | Monitor drug levels |
| 30–59 | Moderate impairment | Dose reduction likely needed |
| 15–29 | Severe impairment | Significant dose adjustment |
| < 15 | Kidney failure / dialysis | Consult nephrology and pharmacy |
How the Cockcroft-Gault result changes with age, sex, weight, and serum creatinine. Each row is calculated as [(140 − Age) × Weight × sex factor] ÷ (72 × Creatinine).
| Patient | Serum creatinine | CrCl | Stage |
|---|---|---|---|
| 40 y, male, 80 kg | 0.9 mg/dL | 123.5 mL/min | Normal |
| 55 y, male, 70 kg | 1.0 mg/dL | 82.6 mL/min | Mild — monitor levels |
| 70 y, female, 60 kg | 1.2 mg/dL | 41.3 mL/min | Moderate — reduce dose |
| 65 y, male, 75 kg | 2.0 mg/dL | 39.1 mL/min | Moderate — reduce dose |
| 80 y, female, 55 kg | 1.5 mg/dL | 26.0 mL/min | Severe — significant adjustment |
CrCl (mL/min) = [(140 − Age) × Weight × 0.85 (if female)] ÷ (72 × Serum Creatinine in mg/dL). Use ideal body weight in obese patients. The formula provides an estimate — actual measured CrCl from a 24-hour urine collection is more precise.
Most dose adjustments are recommended when CrCl drops below 50–60 mL/min for moderate risk drugs, and below 30 mL/min for most renally-cleared medications. Always consult a current drug reference (BNF, Micromedex, or pharmacy) for specific dose adjustment recommendations.
A normal creatinine clearance is roughly 90–120 mL/min in healthy adults, and is generally higher in men than women. CrCl declines naturally with age. 60–89 mL/min suggests mild impairment, 30–59 moderate, 15–29 severe, and below 15 mL/min indicates kidney failure.
Use actual body weight for most patients. In obese patients, ideal or adjusted body weight is generally preferred, because actual weight overestimates clearance. In underweight patients, use actual body weight. When in doubt, follow your local pharmacy protocol.