Estimating kidney function from creatinine
Enter the serum creatinine printed on your lab report together with your age and sex, and this page returns an estimated glomerular filtration rate in mL/min/1.73 m², indexed to a body surface area of 1.73 m². It also prints the constants it used and which exponent branch your value fell into, so the arithmetic is visible rather than hidden.
The equation used is the CKD-EPI 2021 creatinine equation (as of October 2026). Creatinine is divided by the sex constant κ; if that ratio is below 1 the sex exponent α applies, and if it is 1 or above the exponent −1.200 applies. An age factor is then multiplied in, and female results are multiplied by 1.012 once more. This is the version with the race variable removed, which a National Kidney Foundation and American Society of Nephrology task force recommended replacing earlier equations with immediately.
The creatinine you enter should come from a standardized (IDMS-traceable) assay. The equation has not been validated in children, in pregnancy, or in acute kidney injury, where kidney function changes quickly. The result is tagged with its KDIGO 2012 GFR category (G1-G5) for reference, decided on the unrounded value. A chronic kidney disease diagnosis also needs the finding to persist for more than 3 months and/or evidence of kidney damage such as albuminuria, so this page does not diagnose disease from one result. An eGFR is an estimate, and judgments about kidney function and treatment are made by clinicians who see the whole set of results.
Frequently asked questions
No. It is an estimate produced by an equation, so muscle mass, diet and assay method can make it differ from a measured rate. When an exact assessment matters, clinicians add other tests.
They are the GFR categories from the KDIGO 2012 guideline: G1 90 or above, G2 60-89, G3a 45-59, G3b 30-44, G4 15-29 and G5 below 15 mL/min/1.73 m². The category is set from the unrounded value. Chronic kidney disease is diagnosed only when kidney damage (such as albuminuria) or an eGFR below 60 persists for more than 3 months, so one result in a category is not a diagnosis.
The equation carries sex-specific constants for κ and α, and it multiplies the female result by 1.012 once more. The same creatinine value therefore lands on a different estimate.