eGFR Calculator

Estimate your glomerular filtration rate with the 2021 CKD-EPI formula and see where your kidney function falls on the clinical scale.

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CKD-EPI 2021 Equation (race-free)

CKD-EPI 2021 · Inker LA et al., N Engl J Med 2021

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Calculation Examples

Calculation Case Result
Creatinine 1.0 mg/dL, Age 45, Male eGFR approx. 95 (Normal function)
Creatinine 1.0 mg/dL, Age 45, Female eGFR approx. 71 (Mildly Decreased)
Creatinine 1.5 mg/dL, Age 70, Male eGFR approx. 50 (Moderately Decreased, stage G3a)
Creatinine 1.8 mg/dL, Age 65, Female eGFR approx. 31 (Moderately Decreased, stage G3b)
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Founder and developer of CalcMate. Builds and maintains every calculator on this site, focusing on formula accuracy and clear, practical results.

How to Use the eGFR Calculator

Enter your age, sex, and the serum creatinine value from your latest blood test. Then pick the unit your lab reports: mg/dL is standard in the United States, and µmol/L is common elsewhere. The conversion is 1 mg/dL = 88.4 µmol/L, so 1.0 mg/dL equals 88.4 µmol/L. Click Calculate.

The result is your estimated GFR in mL/min/1.73 m² with its category: Normal (90 or above), Mildly Decreased (60-89), Moderately Decreased (30-59), Severely Decreased (15-29), or Kidney Failure (below 15). One result is a snapshot, not a diagnosis. KDIGO defines chronic kidney disease (CKD) by an eGFR below 60 that lasts more than 3 months, or by other signs of kidney damage such as albumin in the urine. This tool gives an estimate for education and does not replace your doctor.

How the 2021 CKD-EPI Equation Works

The calculator uses the 2021 CKD-EPI creatinine equation, which the NKF-ASN Task Force recommended in 2021 (Inker et al., New England Journal of Medicine, 2021) as a race-free replacement for the 2009 version. It estimates how much blood your kidneys filter from serum creatinine, age, and sex. Sex matters because creatinine comes from muscle, so the equation uses a different reference level for women and men.

Example: a 45-year-old man with creatinine 1.0 mg/dL gets an eGFR of about 95. A 45-year-old woman with the same creatinine gets about 71, because her reference level is lower. CKD-EPI shows less bias than the older MDRD equation, especially above 60 mL/min/1.73 m² (Levey et al., 2009). Creatinine still has limits: muscle mass, creatine supplements, and rapidly changing kidney function all distort it. KDIGO 2024 suggests adding cystatin C when creatinine alone may mislead.

CKD stages chart showing eGFR ranges from normal kidney function to kidney failure

Useful Tips 💡

  • Use results from the same lab when you can. Methods differ slightly between labs, so a trend from one lab is cleaner.
  • Pair eGFR with a urine albumin test. Albumin in the urine can signal kidney damage even when eGFR looks normal.
  • Repeat the test every 3-12 months, or at the interval your doctor recommends, to spot trends over time.

📋Steps to Calculate

  1. Enter your age, sex, and serum creatinine value.

  2. Select the creatinine unit: mg/dL or µmol/L.

  3. Click Calculate to see your eGFR result and CKD stage.

Mistakes to Avoid ⚠️

  1. Mixing up units. Typing 88 (µmol/L) into the mg/dL field instead of 1.0 returns an eGFR below 1, which is clearly wrong.
  2. Treating a single reading as a diagnosis. CKD needs an eGFR below 60 for more than 3 months, or other markers of kidney damage.
  3. Assuming eGFR above 90 means healthy kidneys. Albumin in the urine (30 mg/g or more) can indicate damage even with a normal eGFR.
  4. Ignoring muscle mass. Bodybuilders and people taking creatine can have high creatinine with normal kidneys, and people with low muscle mass can look better than they are.

Practical Applications📊

  1. Track the trend across routine blood tests. KDIGO calls a sustained drop of more than 5 mL/min/1.73 m² per year rapid progression, so a fall from 85 to 70 over 2 years deserves attention.

  2. Read one result in context. A man with creatinine 0.9 mg/dL has an eGFR near 118 at age 30 and near 92 at age 70, since the equation builds in an age decline of about 0.6% per year.

  3. Prepare for an appointment. Bring your last 3 results and ask whether you need a urine albumin test, because KDIGO stages CKD by eGFR and albuminuria together.

Questions and Answers

Is the CKD-EPI formula accurate for everyone?

No. The 2021 CKD-EPI creatinine equation is validated for adults 18 and older, and it is less reliable in several groups. These include pregnancy, children (who use pediatric equations), very high or very low muscle mass, and rapidly changing kidney function such as acute kidney injury, because the equation assumes creatinine is stable. In these cases clinicians often add cystatin C, which does not depend on muscle mass, and KDIGO 2024 recommends combining creatinine and cystatin C when precision matters.

What does a low eGFR result mean?

An eGFR below 60 mL/min/1.73 m² for more than 3 months meets the KDIGO definition of CKD. KDIGO stages it as G3a (45-59), G3b (30-44), G4 (15-29), and G5 (below 15, kidney failure). Waste products like urea and creatinine build up as filtration falls. Below 30 you should be under specialist care, and below 15 your doctor will discuss dialysis or a transplant. Treat a single low value as a reason to repeat the test, not as a diagnosis.

What formula does the eGFR calculator use?

The calculator applies the 2021 CKD-EPI creatinine equation: \[\text{eGFR} = 142 \times \min(S_{cr}/\kappa,\ 1)^{\alpha} \times \max(S_{cr}/\kappa,\ 1)^{-1.200} \times 0.9938^{\text{Age}} \times 1.012 \text{ [if female]}\] where \(S_{cr}\) is serum creatinine in mg/dL, \(\kappa\) is 0.7 for females and 0.9 for males, and \(\alpha\) is -0.241 for females and -0.302 for males. For a 45-year-old man with \(S_{cr} = 1.0\): \((1.0/0.9)^{-1.2} \approx 0.881\) and \(0.9938^{45} \approx 0.756\), so \(142 \times 0.881 \times 0.756 \approx 95\). The 2021 version removes the race coefficient, because race is a social category and not a biological measure of kidney function.

What is a normal eGFR by age, and how does it change over time?

A healthy young adult usually has an eGFR above 100 mL/min/1.73 m², and it declines slowly with age. The 2021 equation builds this in with the factor \(0.9938^{\text{Age}}\), a drop of about 0.6% per year. For a man with creatinine 0.9 mg/dL, the result is about 118 at age 30, 104 at 50, 98 at 60, and 92 at 70. Under KDIGO, 90 and above is category G1 and 60-89 is G2, but neither means CKD unless another marker of kidney damage is present.

What is an eGFR calculator and why does it matter for kidney health?

An eGFR calculator estimates how much blood your kidneys filter each minute, scaled to 1.73 m² of body surface area, from serum creatinine, age, and sex. It matters because CKD usually causes no symptoms until it is advanced. The CDC estimates that about 14% of US adults have CKD, and about 87% of adults with CKD do not know it. A falling trend, such as 85 to 70 in 2 years (7.5 per year, above the KDIGO rapid-progression threshold of 5), gives time to act on blood pressure, blood sugar, diet, and medication.
Disclaimer: This calculator is designed to provide helpful estimates for informational purposes. While we strive for accuracy, financial (or medical) results can vary based on local laws and individual circumstances. We recommend consulting with a professional advisor for critical decisions.