Creatinine Clearance Calculator (Cockcroft-Gault)
Estimate creatinine clearance rate (CrCl) in mL/min using age, body weight, sex, and serum creatinine. This is commonly used as a renal function calculator for medication dosing.
Medical disclaimer: This tool is for educational use and quick screening only. It does not replace clinical judgment, lab interpretation, or advice from your healthcare professional.
What is creatinine clearance?
Creatinine clearance (CrCl) is an estimate of how well your kidneys filter creatinine from the blood. Creatinine is a waste product generated by normal muscle metabolism. Because the kidneys remove it from circulation, creatinine levels can help estimate renal function.
In practice, clinicians often use CrCl when adjusting doses for medications that are cleared by the kidneys. A lower clearance value may indicate reduced kidney function and can change treatment decisions.
How this creatinine clearance rate calculator works
Cockcroft-Gault formula
This calculator uses the Cockcroft-Gault equation:
CrCl (mL/min) = ((140 − age) × weight in kg) / (72 × serum creatinine in mg/dL)
For females, the result is multiplied by 0.85.
This formula remains widely used in pharmacology because many drug-dosing recommendations are based on Cockcroft-Gault creatinine clearance.
Unit conversion included automatically
- If weight is entered in pounds, it is converted to kilograms.
- If serum creatinine is entered in µmol/L, it is converted to mg/dL using
mg/dL = µmol/L ÷ 88.4. - If height is provided, body surface area (BSA) is estimated with Mosteller’s formula for optional normalization.
How to use the calculator correctly
- Enter age in years.
- Select biological sex as used by the formula.
- Enter current body weight and choose unit (kg or lb).
- Enter serum creatinine from your latest lab report and select the correct unit.
- Optionally enter height to see BSA-normalized clearance.
- Click Calculate Clearance to view your result and interpretation.
Interpreting your creatinine clearance result
The calculator provides a rough interpretation band. A common framework is:
- ≥ 90 mL/min: generally normal or high clearance
- 60–89 mL/min: mildly reduced kidney function
- 30–59 mL/min: moderately reduced function
- 15–29 mL/min: severely reduced function
- < 15 mL/min: very severe reduction / kidney failure range
These bands are not diagnostic on their own. Diagnosis of chronic kidney disease requires broader clinical context, repeat testing, and often urine studies.
Creatinine clearance vs eGFR
People often compare a kidney function calculator result to eGFR from lab reports. They are related but not identical:
- CrCl (Cockcroft-Gault): often preferred for medication dosing guidance.
- eGFR (CKD-EPI or similar): commonly reported by labs for CKD screening/staging.
Because formulas differ, values may not match exactly. A clinician determines which estimate is most appropriate for your situation.
Common factors that affect accuracy
- Very low or very high muscle mass
- Rapidly changing kidney function (acute illness)
- Edema, dehydration, or unusual body composition
- Pregnancy
- Extremes of age and severe chronic illness
In these settings, additional testing (including measured clearance or cystatin C-based estimates) may be considered.
When to seek medical advice
Contact a healthcare professional if you have:
- Persistently abnormal serum creatinine or CrCl results
- Swelling, reduced urine output, blood in urine, or persistent fatigue
- Diabetes, hypertension, heart failure, or other kidney risk factors
- Questions about safe drug dosing with reduced renal function
Frequently asked questions
Is this the same as a 24-hour urine creatinine clearance test?
No. This calculator gives an estimated creatinine clearance from blood creatinine and demographics. A 24-hour urine test is a direct measurement approach and can differ.
Can I use this for medication decisions by myself?
No. Drug dosing should be confirmed by a licensed clinician or pharmacist, especially for narrow therapeutic index medications.
Why is female sex multiplied by 0.85 in the formula?
The original Cockcroft-Gault model adjusts for average differences in creatinine generation from muscle mass between sexes.
Bottom line
This creatinine clearance rate calculator provides a fast, practical estimate of renal filtration capacity using the Cockcroft-Gault equation. It is useful for education and preliminary screening, but final interpretation should always be made with clinical context and professional medical guidance.