Creatinine Clearance Calculator (Cockcroft-Gault)
Use this tool to estimate creatinine clearance (CrCl) in mL/min. This estimate is commonly used for medication dosing in adults.
What is the Cockcroft-Gault calculator?
The Cockcroft-Gault calculator estimates creatinine clearance (CrCl), a practical marker of kidney filtration used in many drug dosing references. While newer equations (like CKD-EPI) are often used to stage chronic kidney disease, Cockcroft-Gault remains widely used when deciding medication doses—especially for drugs with renal elimination.
The Cockcroft-Gault formula
This page uses the classic equation:
For males: CrCl = ((140 − age) × weight in kg) ÷ (72 × serum creatinine in mg/dL)
For females: CrCl = male result × 0.85
If your creatinine is entered in µmol/L, it is converted to mg/dL first (mg/dL = µmol/L ÷ 88.4).
How to use this calculator correctly
- Enter age in years.
- Select sex at birth (the original formula applies a 0.85 factor for females).
- Enter body weight in kilograms.
- Enter serum creatinine and choose the right unit.
- Optionally enter height to estimate BSA-normalized output.
- Click Calculate to view CrCl and interpretation.
About weight selection
A key source of variation is which weight is used (actual body weight, ideal body weight, or adjusted body weight). Different institutions apply different protocols for obesity or underweight states. If you are calculating for medication dosing, follow your local guideline or pharmacist recommendation.
How to interpret your result
The calculator provides an interpretation band for quick context:
- ≥ 90 mL/min: Normal or high kidney function range.
- 60–89 mL/min: Mild reduction.
- 45–59 mL/min: Mild to moderate reduction.
- 30–44 mL/min: Moderate to severe reduction.
- 15–29 mL/min: Severe reduction.
- < 15 mL/min: Kidney failure range.
These ranges are informational. Medication package inserts may use specific CrCl thresholds (for example, cutoffs at 50, 30, or 15 mL/min) and should be followed directly.
Cockcroft-Gault vs eGFR (CKD-EPI): when each is used
Cockcroft-Gault
- Traditionally used for renal drug dosing.
- Produces mL/min (not always normalized to body surface area).
- Sensitive to body weight input.
CKD-EPI eGFR
- Commonly reported by laboratories automatically.
- Used for CKD detection and staging.
- Reported as mL/min/1.73 m².
In clinical practice, both may be reviewed together. Dosing references, trial criteria, and institutional policy determine which value takes priority.
Common pitfalls and limitations
- Rapidly changing creatinine: Equation assumptions break when kidney function is not at steady state.
- Extremes of muscle mass: Very low or high muscle mass can distort creatinine-based estimates.
- Elderly and frail patients: “Normal” serum creatinine can still mask reduced kidney function.
- Pregnancy: The equation is not validated for routine obstetric use.
- Body composition extremes: Obesity, edema, and amputation may require individualized methods.
Worked example
Suppose a 68-year-old female weighs 62 kg with serum creatinine 1.2 mg/dL:
- Male-equivalent step: ((140 − 68) × 62) ÷ (72 × 1.2) = 51.7 mL/min
- Female adjustment: 51.7 × 0.85 = 44.0 mL/min
This falls in a moderate-to-severe reduction range and may prompt renal dose adjustment depending on the medication.
Frequently asked questions
Is this calculator for children?
No. Cockcroft-Gault is an adult equation. Pediatric renal estimation usually uses other formulas such as the Schwartz equation.
Can I use this for diagnosis?
It is best used as an estimate for clinical decision support. Diagnosis requires a broader evaluation (trends, urinalysis, imaging, comorbidities, and clinician review).
Should I repeat the calculation over time?
Yes. Kidney function is dynamic. Recalculation is often appropriate when labs, hydration, medications, or acute illness change.
Educational note: Always discuss important kidney or dosing decisions with a licensed healthcare professional.