Creatinine Clearance Calculator
Creatinine clearance estimates how quickly the kidneys filter creatinine out of the blood, and it is one of the oldest, most widely taught measures of kidney function. This calculator uses the Cockcroft-Gault equation, the formula still referenced in many drug-dosing tables, to estimate clearance in mL/min from your age, weight, serum creatinine and sex. Enter the four values to see an instant estimate. It is built for learning and quick checks, not for diagnosis or treatment decisions.
How to estimate creatinine clearance
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1
Enter age and weight
Age in years and body weight in kilograms. Both feed directly into the Cockcroft-Gault formula.
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2
Add serum creatinine and sex
Serum creatinine in mg/dL from a recent blood test, and tick Female to apply the 0.85 correction factor.
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3
Read the estimate
The result is creatinine clearance in mL/min, shown instantly alongside the educational-use note.
The Cockcroft-Gault formula explained
The Cockcroft-Gault equation (1976) estimates creatinine clearance (CrCl) from four bedside variables. For serum creatinine measured in mg/dL:
CrCl (mL/min) = ((140 − age) × weight in kg) / (72 × serum creatinine) × (0.85 if female)
The intuition: younger people and heavier people produce more muscle-derived creatinine, so a given blood level reflects faster filtering. The 0.85 factor for women adjusts for lower average muscle mass.
Worked example
A 50-year-old man weighing 70 kg with a serum creatinine of 1.0 mg/dL:
- Numerator: (140 − 50) × 70 = 90 × 70 = 6300
- Denominator: 72 × 1.0 = 72
- CrCl ≈ 6300 ÷ 72 ≈ 87.5 mL/min
If the same patient were female, multiply by 0.85 → ≈ 74.4 mL/min.
How the inputs move the result
| Change in input | Effect on estimated CrCl |
|---|---|
| Older age | Lower (140 − age shrinks) |
| Higher body weight | Higher |
| Higher serum creatinine | Lower (it is the divisor) |
| Female sex | ×0.85, so lower |
Pitfalls to keep in mind
- Weight matters. Cockcroft-Gault uses actual body weight, but in very obese or very lean patients clinicians often substitute ideal or adjusted body weight, results can differ a lot.
- Not the same as eGFR. Modern labs report eGFR from CKD-EPI; Cockcroft-Gault tends to estimate higher and is unindexed to body surface area.
- Unstable creatinine. The formula assumes a steady state. In acute kidney injury, when creatinine is rising or falling fast, the estimate is unreliable.
- Units. This calculator expects creatinine in mg/dL. If your lab reports µmol/L, divide by 88.4 first (1 mg/dL ≈ 88.4 µmol/L).
Frequently Asked Questions
No. This tool is for educational use only and is not a substitute for professional medical advice, diagnosis or treatment. Always consult a qualified clinician for decisions about kidney function, medication dosing or any health concern.
Your age, weight, creatinine and sex are sent to the server to compute the estimate, and they can be carried in the page link as you move through the steps. They are not stored, saved or shared.
Healthy adults often fall roughly in the 90-140 mL/min range, with women slightly lower than men on average, and values declining with age. These are general reference points only; your clinician interprets the number in the context of your full picture.
They use different equations and assumptions. Cockcroft-Gault estimates creatinine clearance from age, weight, creatinine and sex, while modern labs report eGFR using CKD-EPI, which is indexed to body surface area. The two will rarely match exactly; many drug-dosing references still specify Cockcroft-Gault.
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