Creatinine Clearance Calculator

Estimate creatinine clearance from common clinical inputs to help assess kidney function.

What This Calculator Does

This creatinine clearance calculator estimates the rate at which the kidneys filter waste from the blood. It uses standard clinical inputs—serum creatinine, age, weight, and sex—to produce an estimated creatinine clearance (CrCl) value in mL/min. This estimate helps clinicians and patients assess kidney function without requiring a 24-hour urine collection.

The calculation follows the Cockcroft-Gault formula, a widely accepted method for estimating glomerular filtration rate (eGFR) in adults. While newer equations exist, Cockcroft-Gault remains commonly used for drug dosing adjustments and initial kidney function screening.

How the Calculation Works

The Cockcroft-Gault formula estimates creatinine clearance using four inputs:

Serum creatinine – the concentration of creatinine in the blood (mg/dL or µmol/L)
Age – kidney function naturally declines with age
Weight – muscle mass affects creatinine production
Sex – males typically have higher muscle mass and creatinine production

The formula is:

CrCl (mL/min) = [(140 − age) × weight (kg)] ÷ [72 × serum creatinine (mg/dL)]

For females, the result is multiplied by 0.85 to account for lower average muscle mass.

This calculator automatically handles unit conversions. If you enter creatinine in µmol/L, it converts to mg/dL before applying the formula.

How to Use the Calculator

Select the patient's sex.
Enter age in years.
Enter weight in kilograms or pounds.
Enter serum creatinine and select the correct unit (mg/dL or µmol/L).
Click Calculate to see the estimated creatinine clearance.

The result displays as a single value in mL/min. No additional interpretation is applied—the calculator returns the raw estimate from the formula.

Understanding the Result

The estimated creatinine clearance value represents the volume of blood plasma cleared of creatinine per minute. Higher values indicate better kidney function. Typical reference ranges vary by age and sex, but general guidelines are:

90–120 mL/min – normal kidney function in young adults
60–89 mL/min – mild decrease, common with aging
30–59 mL/min – moderate decrease
15–29 mL/min – severe decrease
Below 15 mL/min – kidney failure

These ranges are general references. Individual results should always be interpreted by a healthcare professional in the context of the patient's overall health, medications, and clinical history.

Important Limitations

The Cockcroft-Gault formula has known limitations that affect accuracy in certain populations:

Obesity – the formula may overestimate CrCl in obese patients because it uses total body weight rather than lean body mass
Elderly patients – may overestimate function due to reduced muscle mass
Pregnancy – not validated for pregnant women
Rapidly changing kidney function – the formula assumes steady-state creatinine, which may not apply in acute kidney injury
Very low muscle mass – amputees, malnourished patients, or those with muscle-wasting conditions may have falsely low creatinine levels

This calculator provides an estimate only. It is not a substitute for measured creatinine clearance via 24-hour urine collection or for other diagnostic tests ordered by a physician.

Common Mistakes to Avoid

Using the wrong creatinine unit – mg/dL and µmol/L differ by a factor of approximately 88.4. Always verify the unit before entering the value.
Entering weight in pounds without converting – the formula requires kilograms. This calculator accepts both, but ensure you select the correct unit.
Applying the formula to children – Cockcroft-Gault is validated for adults aged 18 and older. Pediatric kidney function estimation requires different equations.
Assuming the result is a measured value – this is an estimate, not a direct measurement. Variability of 10–20% is expected.

When This Calculator Is Used

Clinicians commonly use estimated creatinine clearance for:

Drug dosing adjustments – many medications require dose modification based on kidney function
Initial kidney function screening – a quick assessment before more detailed testing
Monitoring chronic kidney disease progression – tracking changes over time
Pre-operative assessment – evaluating kidney function before surgery or contrast imaging

In each case, the estimate provides actionable information quickly, without requiring a 24-hour urine collection.

Frequently Asked Questions

What is the difference between creatinine clearance and eGFR?

Creatinine clearance (CrCl) estimates how much creatinine the kidneys filter per minute. Estimated glomerular filtration rate (eGFR) is a broader estimate of overall kidney function, typically calculated using the MDRD or CKD-EPI equations. CrCl is often preferred for drug dosing, while eGFR is more commonly used for staging chronic kidney disease.

Why does the formula multiply by 0.85 for females?

Females generally have lower muscle mass than males, which means they produce less creatinine from muscle turnover. The 0.85 adjustment accounts for this difference, preventing overestimation of kidney function in female patients.

Can I use this calculator if I have acute kidney injury?

The Cockcroft-Gault formula assumes steady-state creatinine levels, which is not the case during acute kidney injury when creatinine is rising or falling rapidly. Results during acute illness may be inaccurate and should not be used for clinical decisions without physician guidance.

What is a normal creatinine clearance for my age?

Normal values decline with age. A 30-year-old may have CrCl around 100–120 mL/min, while a 70-year-old may have 60–80 mL/min. This decline is considered normal aging, not necessarily kidney disease. Your doctor can interpret your result in the context of your overall health.

Does diet affect creatinine clearance results?

Yes. High meat intake, creatine supplements, and dehydration can temporarily raise serum creatinine, leading to a lower estimated CrCl. Conversely, a vegetarian diet may lower creatinine levels. For the most accurate assessment, labs are typically drawn after a period of stable diet and hydration.