Your kidneys filter waste from the blood, and the single number that describes how well they do that job is the estimated glomerular filtration rate, or eGFR. A lab usually prints it next to your creatinine result, but most reports give you the number without explaining what it means, where it came from, or what you should do next. This eGFR calculator takes the values on your blood-test report and runs them through the current race-free CKD-EPI 2021 equation — the same formula recommended by the National Kidney Foundation and the American Society of Nephrology — then maps the result to a chronic kidney disease (CKD) stage so you can see whether you are in the normal range, in early-stage kidney disease, or need to talk to a doctor promptly.
About 15% of US adults are estimated to have some stage of chronic kidney disease, and most do not know it — which is why understanding your own number matters. Adjust the four fields and your eGFR, CKD stage, and recommended next step update instantly.
How to Use
- Enter your Serum Creatinine exactly as it appears on your lab report, in mg/dL. If your lab reports micromoles per liter (µmol/L), divide by 88.4 to convert to mg/dL first.
- Type your Age in years. The equation is built for adults 18 and older; for children, a separate pediatric GFR estimate is used.
- Choose your Sex (female or male). This selects the constants the equation uses and, for women, applies the small 1.012 adjustment.
- Set Race to non-Black or Black if you want to reproduce an older lab report. The 2021 equation is race-free, so this choice does not move your result — it exists only so you can compare against reports issued before the 2021 update.
- Read the result card: your eGFR (mL/min/1.73 m²), the CKD stage code (1 = G1 normal at/above 90, 2 = G2 mild 60–89, 3 = G3a 45–59, 4 = G3b 30–44, 5 = G4 severe 15–29, 6 = G5 failure under 15), and how many points you sit below the normal floor of 90.
A normal eGFR is roughly 90 or above, but the number naturally drifts down with age — a value of 70 in a 70-year-old is not the same warning it would be in a 30-year-old. The equation already accounts for age, so you do not need to "adjust" the result yourself.
The CKD-EPI 2021 Equation
Your eGFR is estimated from serum creatinine (the waste product your kidneys clear), your age, and your sex:
eGFR = 142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^(−1.200) × 0.9938^Age × (1.012 if female)
Where:
- Scr is your serum creatinine in mg/dL.
- κ (kappa) is 0.7 for women and 0.9 for men.
- α (alpha) is −0.241 for women and −0.302 for men.
- The 0.9938^Age term captures the gradual decline in kidney filtration that comes with normal aging.
- The 1.012 multiplier is applied for women.
The 2021 update removed the old race coefficient that had been part of the 2009 equation, after the NKF and ASN concluded that race is a social construct, not a biological input. That is why your race selection here does not change the number.
What the CKD Stages Mean
The Kidney Disease: Improving Global Outcomes (KDIGO) guidelines split kidney function into six stages:
- G1 — eGFR ≥ 90: Normal or high filtration. No visible kidney damage by eGFR alone.
- G2 — eGFR 60–89: Mildly reduced. Common with age; worth monitoring.
- G3a — eGFR 45–59: Mild-to-moderate reduction.
- G3b — eGFR 30–44: Moderate-to-severe reduction.
- G4 — eGFR 15–29: Severe reduction; nephrology referral recommended.
- G5 — eGFR < 15: Kidney failure; dialysis or transplant evaluation may be needed.
A single eGFR below 60 is not automatically CKD — the diagnosis requires the reduced rate (or other markers of damage, such as protein in the urine) to persist for about three months. One borderline result usually means "repeat the test," not "you have kidney disease."
Examples
Example 1 — A typical 50-year-old woman. Creatinine 1.0 mg/dL, age 50, female. The calculator returns an eGFR of about 69 mL/min/1.73 m², stage G2, "Mildly reduced kidney function." Because G2 in a 50-year-old is common and not alarming, the recommended next step is a routine check-up and a repeat test in 6–12 months.
Example 2 — A healthy 40-year-old man. Creatinine 0.9 mg/dL, age 40, male. eGFR comes out near 111, stage G1, "Normal or high kidney function." No action beyond routine screening.
Example 3 — A 70-year-old woman with rising creatinine. Creatinine 1.3 mg/dL, age 70, female. eGFR drops to roughly 44, stage G3b, "Moderate-to-severe reduction." The recommended next step is to ask the doctor for a urine albumin-to-creatinine ratio (UACR) and to repeat the eGFR within 3 months, because G3b is the range where referral to a nephrologist is commonly considered.
FAQ
What is a normal eGFR?
A normal eGFR is generally 90 mL/min/1.73 m² or higher. Values between 60 and 89 are considered mildly reduced and are common, especially as people age. A result below 60 on two occasions spaced at least three months apart is the threshold used to define chronic kidney disease.
How is eGFR calculated from creatinine?
eGFR uses the CKD-EPI 2021 equation, which plugs your serum creatinine, age, and sex into a published formula with fixed constants. The lab automatically performs this calculation when it measures creatinine, which is why the result appears on your report even though you did not order a separate "eGFR test."
Why does my eGFR go down as I get older?
Kidney filtration naturally declines with age, and the equation already includes an age term (0.9938 raised to your age). That means a creatinine that looks "normal" for a young adult may hide a reduced eGFR in an older person — which is exactly why the eGFR estimate is more informative than looking at creatinine alone.
Does race affect my eGFR?
No. The current 2021 CKD-EPI equation is race-free, following the joint NKF/ASN recommendation that race is not a biological measure of kidney function. Older reports from 2009–2021 applied a Black-race coefficient, which is why this calculator keeps a race selector only so you can compare your current result against older lab values.
What should I do if my eGFR is below 60?
A single result below 60 should be repeated, ideally along with a urine albumin-to-creatinine ratio (UACR) that checks for protein leakage. If the reduced eGFR persists for three months, or if the UACR is elevated, your doctor will classify the CKD stage and may recommend blood-pressure control, diabetes management, dietary changes, or a nephrology referral.
Can I improve my eGFR?
An eGFR cannot be raised back to normal once true kidney damage has occurred, but controlling blood pressure, blood sugar, cholesterol, and salt intake, avoiding regular NSAID pain relievers, and not smoking can slow further decline. Many people with stage G2 or G3 CKD live full lives with good medical management.
Disclaimer
This eGFR calculator is provided for informational purposes only and is not medical advice. It estimates kidney function from the CKD-EPI 2021 equation and is intended for education and self-checking, not for diagnosis or treatment decisions. eGFR can be affected by dehydration, recent illness, diet, muscle mass, and medications, and a single result does not diagnose CKD. Always interpret your lab results with a qualified healthcare professional who knows your full medical history.