Kidney Function Calculator (eGFR + CrCl)
Estimate kidney function using serum creatinine. This tool calculates:
- eGFR (CKD-EPI 2021): commonly used to stage chronic kidney disease
- Creatinine Clearance (Cockcroft-Gault): often used for medication dosing
Educational use only. This calculator does not replace clinical judgment. Pregnancy, acute kidney injury, unusual muscle mass, amputations, and rapidly changing creatinine can make estimates less accurate.
What is a kidney calculator?
A kidney calculator estimates how well your kidneys are filtering blood. The most common estimate is called eGFR (estimated glomerular filtration rate), reported as mL/min/1.73m². Clinicians also use creatinine clearance (CrCl) in some settings, especially when adjusting doses for certain medications.
These are estimates, not direct measurements. They are helpful for screening and monitoring trends, but they should always be interpreted with your medical history, urine testing, blood pressure, medications, and other labs.
How this calculator works
1) eGFR (CKD-EPI 2021)
The CKD-EPI 2021 creatinine equation is a race-free equation now widely used in clinical labs. It uses age, sex at birth, and serum creatinine to estimate filtration rate.
2) Creatinine Clearance (Cockcroft-Gault)
Cockcroft-Gault uses age, weight, sex, and creatinine. While older than CKD-EPI, it remains relevant because many drug labels still reference creatinine clearance for dosing.
How to interpret your result
eGFR is commonly grouped into categories called G-stages:
- G1: ≥ 90 (normal or high, if other kidney damage markers are present)
- G2: 60–89 (mildly decreased)
- G3a: 45–59 (mild to moderate decrease)
- G3b: 30–44 (moderate to severe decrease)
- G4: 15–29 (severely decreased)
- G5: < 15 (kidney failure range)
Important: eGFR stage alone is not the whole story. Doctors also use urine albumin (ACR), trend over time, and symptoms. A single value should generally be confirmed with repeat testing.
When estimates can be inaccurate
- Rapidly changing kidney function (for example, dehydration or acute illness)
- Very high or very low muscle mass
- Bodybuilding, severe malnutrition, or limb amputation
- Pregnancy
- Certain medications affecting creatinine handling
Practical kidney health checklist
- Monitor blood pressure and keep it in your target range
- Control blood sugar if you have diabetes
- Avoid unnecessary NSAID use unless advised by your clinician
- Stay hydrated and discuss protein/salt goals with your care team
- Get regular labs if you have CKD risk factors
Frequently asked questions
Is eGFR the same as measured GFR?
No. eGFR is estimated from blood creatinine. Measured GFR requires specialized testing and is used in select situations.
Can eGFR improve?
Sometimes, yes—especially if a temporary factor (like dehydration or medication effects) caused a dip. In chronic kidney disease, the goal is often to slow progression and reduce complications.
Should I worry about one abnormal value?
One value is a signal to follow up, not a diagnosis by itself. Most guidelines require persistent abnormalities over at least 3 months before labeling chronic kidney disease.