GFR Calculator

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Medical disclaimer: This calculator is for informational and educational purposes only and is not medical advice. Kidney function must be interpreted by a qualified healthcare professional. Always consult your doctor for medical decisions.

Age (years)

Gender

Serum creatinine (mg/dL)

From a recent blood test. Uses the race-free CKD-EPI 2021 equation.

About GFR Calculator

What is the GFR Calculator?

The GFR Calculator is a free online medical tool that estimates your Glomerular Filtration Rate, the best overall measure of kidney function. GFR describes how many milliliters of blood your kidneys filter per minute, and doctors use it to detect, stage and monitor chronic kidney disease. A normal eGFR is 90 or above, while values below 60 sustained over three months indicate chronic kidney disease.

This calculator uses the CKD-EPI 2021 creatinine equation, the current clinical standard adopted worldwide. It combines your serum creatinine level with your age and sex to estimate filtration rate, since creatinine alone is misleading: the same value means different kidney function in a young man versus an elderly woman. Results include the CKD stage mapping so you can understand where you stand.

How to Use the GFR Calculator

Get your creatinine result: Find serum creatinine (mg/dL) on your recent blood test report.
Enter your age: Type your age in years, since kidney function naturally declines with age.
Select your sex: Choose male or female, as the equation uses different constants.
Enter creatinine: Type the value exactly as reported by your lab.
Read your eGFR: Your estimated filtration rate appears with its CKD stage and what each stage means.

Key Benefits

CKD-EPI 2021 equation: Uses the current race-free clinical standard.
CKD staging: Maps your result to the standard 1-to-5 kidney disease stages.
Context included: Explains what each range means in plain language.
Trend tracking: Recalculate with each new lab panel to watch your trajectory.
Free with no signup: Private calculations, your health data never leaves your browser.

Pro Tips

One reading is not a diagnosis: CKD requires persistently low eGFR over three months plus clinical review.
Avoid NSAIDs: Ibuprofen and similar painkillers can harm kidneys. Discuss pain relief with your doctor.
Control blood pressure and sugar: These are the two biggest drivers of kidney decline, and managing them protects GFR.
Stay hydrated, skip the extremes: Normal hydration supports kidneys. Excessive water or supplement loading does not improve GFR.

Frequently Asked Questions

What is a normal GFR?

90 mL/min/1.73m2 or above is considered normal. It naturally declines about 1 point per year after age 40.

What GFR indicates kidney disease?

An eGFR below 60 sustained for three months, or any eGFR with signs of kidney damage like protein in urine, indicates chronic kidney disease.

Can GFR improve?

Sometimes. Treating the underlying cause, controlling blood pressure and diabetes, and stopping harmful medications can stabilize or modestly improve it.

Why not just use creatinine alone?

Creatinine depends on muscle mass, age and sex. The equation adjusts for these so the result reflects true filtration, not just body size.

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Medical Disclaimer: This calculator is for informational and educational purposes only and is not medical advice. eGFR is an estimate that must be interpreted by a qualified healthcare professional alongside urine tests and your full history. Always consult your doctor about kidney health.

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