eGFR Calculator (CKD-EPI 2021)
Estimated glomerular filtration rate from serum creatinine using the current race-free CKD-EPI 2021 equation — with the KDIGO G stage for the result.
The 2021 CKD-EPI equation is the race-free standard for estimating kidney function from creatinine. It was developed by the CKD Epidemiology Collaboration and recommended by the National Kidney Foundation and the American Society of Nephrology for routine reporting, replacing the older equations that included a race coefficient. Enter serum creatinine (mg/dL or µmol/L), age, and sex for the eGFR in mL/min/1.73 m² and the corresponding KDIGO G category.
Calculate eGFR
The equation and the G stages
The CKD-EPI 2021 creatinine equation is: eGFR = 142 × min(Scr/κ, 1)α × max(Scr/κ, 1)−1.200 × 0.9938Age × 1.012 (if female), where κ is 0.7 for females and 0.9 for males, and α is −0.241 for females and −0.302 for males. There is no race term. Creatinine reported in µmol/L is converted by dividing by 88.4.
| KDIGO G stage | eGFR (mL/min/1.73 m²) | Description |
|---|---|---|
| G1 | ≥ 90 | Normal to high |
| G2 | 60–89 | Mildly decreased |
| G3a | 45–59 | Mildly to moderately decreased |
| G3b | 30–44 | Moderately to severely decreased |
| G4 | 15–29 | Severely decreased |
| G5 | < 15 | Kidney failure |
Creatinine-based estimates have known limits: muscle mass extremes, amputation, body-building, creatine supplements, and rapidly changing kidney function (AKI) all distort the result, and estimating equations are imprecise near the normal range. Where the number drives a major decision — chemotherapy dosing, transplant evaluation, kidney-donor assessment — guidelines point to confirmatory testing with cystatin C or a measured GFR. Practices documenting CKD also need the staging right for coding: the G stage maps directly to the CKD stage documented and billed, which is why our nephrology billing workflow double-checks stage documentation against the lab trend.
Disclaimer: This calculator is educational only and is not medical advice. It does not replace clinical judgment, a full patient assessment, or current KDIGO guidance. Confirm inputs and interpret the result in the context of the individual patient.
Frequently asked questions
Why does the 2021 equation not ask for race?
The CKD-EPI 2021 equation was refit without race after the National Kidney Foundation and American Society of Nephrology recommended removing race from eGFR reporting. It uses only creatinine, age, and sex, and it is the equation US laboratories have adopted for routine reporting.
Does an eGFR of 55 mean the patient has CKD stage G3a?
Not by itself. A single eGFR of 55 falls in the G3a range, but chronic kidney disease requires the abnormality to persist for more than 3 months. Confirm with repeat testing, review the trend, and check the urine albumin-creatinine ratio before assigning a CKD stage.
When should cystatin C or a measured GFR be used instead?
When the creatinine-based estimate may be inaccurate — extremes of muscle mass, amputation, unusual diet, or AKI — or when the result drives a high-stakes decision such as drug dosing with a narrow margin, transplant evaluation, or living-donor assessment. The CKD-EPI creatinine-cystatin equations improve accuracy in many of these situations.