Estimated with Cockcroft-Gault (1976). This is an estimate, not a measured clearance: it can over- or underestimate with obesity, low muscle mass, advanced age, edema, pregnancy, or a non-steady serum creatinine. It is also not a drug-dosing calculator — dosing decisions belong to a clinician or pharmacist.
Kidney function bands
Your CrCl is mapped to these bands, aligned with KDIGO staging thresholds (KDIGO formally splits the 30–59 range into G3a 45–59 and G3b 30–44):
| CrCl (mL/min) | Band | Meaning |
|---|---|---|
| ≥ 90 | Normal (G1) | Normal kidney function |
| 60 – 89 | Mild decrease (G2) | Mildly decreased function |
| 30 – 59 | Moderate decrease (G3) | Moderately decreased function |
| 15 – 29 | Severe decrease (G4) | Severely decreased function |
| < 15 | Kidney failure (G5) | Kidney failure range |
The formula
CrCl (mL/min) = (140 − age) × weight (kg) / (72 × serum creatinine [mg/dL]), multiplied by 0.85 for women. If creatinine is entered in µmol/L it is first divided by 88.4 to convert to mg/dL. Derived by Cockcroft and Gault, Nephron 1976.
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Frequently asked questions
What is the Cockcroft-Gault formula for creatinine clearance?
The Cockcroft-Gault equation, published in 1976, is: CrCl (mL/min) = (140 minus age in years) times weight in kilograms, divided by (72 times serum creatinine in mg/dL). For women, multiply the result by 0.85 to account for lower average muscle mass. It estimates how many milliliters of blood plasma the kidneys clear of creatinine per minute.
What is a normal creatinine clearance value?
A creatinine clearance of 90 mL/min or higher is considered normal. Values of 60 to 89 indicate a mild decrease, 30 to 59 a moderate decrease, 15 to 29 a severe decrease, and below 15 mL/min is in the kidney failure range. These bands follow KDIGO staging thresholds used for chronic kidney disease.
How do I convert serum creatinine from µmol/L to mg/dL?
Divide the µmol/L value by 88.4. For example, 106.08 µmol/L divided by 88.4 equals 1.2 mg/dL. The number 88.4 comes from the molecular weight of creatinine (113.12 g/mol): 1 mg/dL equals 88.4 µmol/L. This calculator does the conversion automatically when you select µmol/L.
How do I convert pounds to kilograms for this calculator?
Divide pounds by 2.20462. For example, 154.32 lb divided by 2.20462 equals 70.0 kg. This calculator does the conversion automatically when you select lb as the weight unit, so you can enter your weight in whichever unit you know.
Can you walk me through a worked example?
Take a 65-year-old man weighing 70 kg with serum creatinine 1.2 mg/dL. Step 1: 140 minus 65 equals 75. Step 2: 75 times 70 equals 5250. Step 3: 72 times 1.2 equals 86.4. Step 4: 5250 divided by 86.4 equals 60.76, rounded to 60.8 mL/min. That falls in the 60 to 89 band, a mild decrease. A woman with identical values would multiply by 0.85, giving 51.6 mL/min, a moderate decrease.
Is creatinine clearance the same as GFR?
No. Creatinine clearance estimates how fast the kidneys clear creatinine, which includes a small amount of tubular secretion, so it can read slightly higher than the true glomerular filtration rate. It is also not normalized to body surface area, unlike eGFR values on a lab report, which usually come from the CKD-EPI equation. Many drug dosing guidelines still reference Cockcroft-Gault, which is why this estimate matters for medication safety discussions with a clinician.
When is the Cockcroft-Gault equation inaccurate?
The equation assumes a steady serum creatinine and average muscle mass for the given weight, so it can overestimate or underestimate in several situations: obesity, since extra fat does not produce creatinine; advanced age or muscle wasting, since less muscle means less creatinine; pregnancy, since kidney filtering increases; edema or fluid overload, since weight is inflated; and acute kidney injury, since creatinine is not at a steady state. Treat the result as an estimate, not a measured value.
Can I use this result to adjust my medication dose?
No. This tool gives an educational estimate only and must not be used to change any dose on your own. Kidney-function-based dose adjustments are made by a doctor or pharmacist using clinical guidelines, the specific drug label, and your full medical picture. This calculator provides zero dosing recommendations by design; bring the number to a professional and ask what it means for you.
Why does the calculator ask for my sex?
The Cockcroft-Gault equation multiplies the result by 0.85 for women because women on average have less skeletal muscle mass than men of the same age and weight, and therefore produce less creatinine. Without this correction the formula would overestimate kidney function in women. The factor applies to biological sex as used in the original 1976 study.
What does CrCl stand for, and is this related to colorectal cancer (CRC)?
CrCl stands for creatinine clearance, an estimate of kidney filtering function. It is unrelated to colorectal cancer, which is sometimes abbreviated CRC. This page uses the URL slug crc for brevity, but the tool is strictly a creatinine clearance calculator using the Cockcroft-Gault equation; it contains no cancer information at all.