GFR Calculator
Estimate your glomerular filtration rate (eGFR) from serum creatinine, age, and sex using the race-free CKD-EPI 2021 formula. eGFR is the key number clinicians use to assess kidney function and stage chronic kidney disease.
How to Use
- Select your sex — the CKD-EPI equation applies a different coefficient for men and women.
- Enter your age in years.
- Enter your serum creatinine in mg/dL — find this on a blood test (metabolic panel) result.
- Read your estimated eGFR in mL/min/1.73 m² and the corresponding CKD stage (1 through 5).
- Compare against the staging chart below to see where your result falls.
Show Work
CKD stages
About the GFR Calculator
Whether you are at a desk or on your phone, the GFR Calculator makes health and fitness tracking easy — and it is completely free. Estimate your glomerular filtration rate (eGFR) from serum creatinine, age, and sex using the race-free CKD-EPI 2021 formula. eGFR is the key number clinicians use to assess kidney function and stage chronic kidney disease.
How it works
Type your numbers into the boxes. The answer shows up right away — you do not have to press a button. If you change a number, the answer changes too. So you can try different numbers and watch what happens, or check an answer you worked out yourself. Just make sure each box has the right kind of number in it.
Want the deeper story? The Knowledge Base explains the ideas behind the tools in more detail.
Frequently Asked Questions
What is eGFR and what does it measure?
Estimated glomerular filtration rate approximates how much blood your kidneys filter per minute, normalized to a standard body surface area of 1.73 m². It is the standard measure of kidney function. A value of 90 or above is generally considered normal; lower values indicate reduced filtering capacity and, if persistent, chronic kidney disease.
What is the CKD-EPI 2021 equation?
CKD-EPI is the equation recommended by major kidney organizations for estimating GFR in adults. The 2021 revision removed the race coefficient that earlier versions used, so the estimate now depends only on creatinine, age, and sex. It tends to be more accurate than the older MDRD equation, especially at higher (near-normal) GFR levels.
Why does serum creatinine matter so much?
Creatinine is a waste product of muscle metabolism that healthy kidneys clear from the blood at a steady rate. When filtration falls, creatinine builds up, so a higher blood creatinine signals lower kidney function. Because creatinine is also affected by muscle mass, very muscular or very frail people can have eGFR estimates that under- or over-state their true kidney function.
What does my CKD stage mean?
Stages run from 1 (eGFR ≥ 90, normal) through 5 (eGFR < 15, kidney failure). Stage 3 is split into 3a (45–59) and 3b (30–44). A single low reading does not by itself mean chronic kidney disease — CKD requires reduced function or kidney damage persisting for at least three months, interpreted alongside urine tests and other findings.
Can I use this result to diagnose kidney disease?
No. This calculator is for informational and educational purposes only and is not medical advice or a diagnosis. eGFR must be interpreted by a clinician together with your history, urine albumin, repeat testing, and other factors. If you have a result that concerns you, discuss it with your doctor.
How do I use the GFR Calculator?
Just type your numbers. The answer shows up right away — there is no button to press. Change anything and it updates by itself.
Is it free? Does it work without internet?
Yes to both. It is free with no sign-up, and once the page has loaded it keeps working even with no internet.
Where does my data go?
Nowhere — every calculation runs on your own device. Nothing you enter is uploaded, logged, or stored.
Common Use Cases
Understanding a blood test
Turn a serum creatinine value from a lab report into an eGFR and CKD stage.
Tracking kidney function over time
Recalculate after each test to watch the trend in your estimated filtration rate.
Preparing for a clinic visit
Get context on your numbers before discussing them with your healthcare provider.
Medication dosing awareness
See why many drugs are dose-adjusted based on kidney function and CKD stage.
Health and nursing study
A reference for learning the CKD-EPI 2021 equation and CKD staging thresholds.
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