GFR Calculator
Use this GFR calculator to estimate your kidney function from creatinine, age, and sex using the current CKD-EPI equation.
Updated October 2, 2026
Medical Disclaimer: This calculator provides a general estimate based on established research and is for educational purposes only, not a substitute for medical advice. Individual results can vary based on health conditions, so consult a qualified healthcare professional or registered dietitian before making significant changes to your diet, exercise, or health routine. Read our full Medical Disclaimer.
How GFR Is Calculated
Glomerular filtration rate (GFR) measures how well your kidneys filter blood. Since directly measuring GFR is impractical outside a clinical lab, this calculator estimates it (eGFR) from a routine blood test, serum creatinine, using the current CKD-EPI equation.
What This Calculator Measures
This estimates kidney filtration function and the corresponding chronic kidney disease (CKD) stage, it does not diagnose kidney disease on its own, which requires clinical evaluation alongside other markers.
The Formula
This calculator uses the 2021 CKD-EPI creatinine equation, the current standard that removed the previous version's race coefficient¹:
Female: eGFR = 142 x min(Scr/0.7, 1)^-0.241 x max(Scr/0.7, 1)^-1.200 x 0.9938^Age x 1.012
Male: eGFR = 142 x min(Scr/0.9, 1)^-0.302 x max(Scr/0.9, 1)^-1.200 x 0.9938^Age
How This Calculator Computes Your Result
Enter your serum creatinine level (from a recent blood test), age, and sex. We apply the appropriate equation above and return your estimated GFR along with your CKD stage.
What Your Result Means
eGFR results are grouped into standard CKD stages²:
G1: 90 or above (normal or high)
G2: 60 to 89 (mildly decreased)
G3a: 45 to 59 (mildly to moderately decreased)
G3b: 30 to 44 (moderately to severely decreased)
G4: 15 to 29 (severely decreased)
G5: under 15 (kidney failure)
A G1 or G2 result alone, without other markers of kidney damage such as protein in the urine, does not by itself meet the formal clinical definition of chronic kidney disease.
Why the Race Coefficient Was Removed
The original CKD-EPI creatinine equation, published in 2009, included a coefficient that adjusted results upward for patients identified as Black, based on average differences observed in the study population used to develop it³. A 2021 joint task force concluded this approach risked both inaccuracy for individuals and reinforcing race as a biological category in a way that wasn't well justified, and developed the race-free version used by this calculator as the new standard¹.
What Can Throw Off Your Result
Because this equation estimates kidney function indirectly, from creatinine, a waste product generated by muscle, anything that changes how much creatinine your muscles produce can shift the result without actual kidney function changing at all. Very high muscle mass, a very high-protein diet, and creatine supplementation can all push creatinine up and make eGFR look lower than it really is, while very low muscle mass can do the opposite⁴.
A Note on Accuracy
This equation assumes stable, steady-state kidney function and is not validated for rapidly changing or acute kidney injury. Results can be skewed by very high or very low muscle mass, high dietary protein intake, or creatine supplementation, independent of actual kidney function. Not validated for pregnant individuals. This is an estimate, not a diagnosis, talk to a doctor about any abnormal result.
Frequently Asked Questions
What is a normal GFR?
A GFR of 90 or above is generally considered normal. Values below 60 for three months or more are a key marker used in diagnosing chronic kidney disease².
What formula does this GFR calculator use?
The 2021 CKD-EPI creatinine equation, the current recommended standard, which does not use a race coefficient¹.
Can muscle mass affect my GFR result?
Yes. Since the equation relies on creatinine, a byproduct of muscle metabolism, very high or very low muscle mass, a high-protein diet, or creatine supplements can skew the estimate independent of actual kidney function⁴.
Is a low eGFR always chronic kidney disease?
Not necessarily on its own. A diagnosis of chronic kidney disease typically requires a reduced eGFR, or other evidence of kidney damage, persisting for three months or more, evaluated by a doctor.
Sources
New Creatinine- and Cystatin C-Based Equations to Estimate GFR without Race, Inker et al., New England Journal of Medicine, 2021
CKD Stages, National Kidney Foundation
A New Equation to Estimate Glomerular Filtration Rate, Levey et al., Annals of Internal Medicine, 2009
Factors Affecting eGFR Accuracy, National Institute of Diabetes and Digestive and Kidney Diseases