eGFR Calculator

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

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 above 90 (Normal function)
Creatinine 1.8 mg/dL, Age 65, Female eGFR approx. 30 (Moderately Decreased)
2021 CKD-EPI equation Current clinical gold standard per NKF and ASN

How to Use the eGFR Calculator

Enter your age, sex, and the serum creatinine value from your most recent blood test. Select the unit your lab uses: mg/dL is standard in the United States, while µmol/L is common in most other countries. Then click Calculate.

The result shows your estimated GFR in mL/min/1.73 m² alongside its clinical classification: Normal (90 or above), Mildly Decreased (60-89), Moderately Decreased (30-59), Severely Decreased (15-29), or Kidney Failure (below 15). A single result is a snapshot, not a diagnosis. Consistent readings below 60 over three or more months are what clinicians use to confirm Chronic Kidney Disease.

Methodology and Scientific Standards

The calculator implements the 2021 CKD-EPI creatinine equation, currently the most accurate non-invasive method for estimating adult renal function. Following updated joint guidelines from the National Kidney Foundation (NKF) and the American Society of Nephrology (ASN), this version removes race-based coefficients to improve diagnostic equity across diverse populations.

Compared to the older MDRD formula, CKD-EPI 2021 shows lower systematic bias and better agreement with directly measured GFR, particularly in the clinically important range above 60 mL/min/1.73 m². This makes it the preferred standard in contemporary nephrology practice worldwide.

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

Useful Tips 💡

  • Always use the creatinine value from your most recent fasting blood draw for the most accurate result.
  • Repeat the calculation every 3-12 months, or at whatever 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. Entering creatinine in µmol/L when the calculator is set to mg/dL, or vice versa, this shifts the result dramatically.
  2. Treating a single eGFR reading as a diagnosis, CKD requires two readings below 60 separated by at least 90 days.
  3. Assuming eGFR above 90 means perfect kidney health, early glomerular damage can hide behind a normal number.
  4. Forgetting that high muscle mass, low muscle mass, or a high-protein diet all affect serum creatinine independently of kidney function.

Practical Applications📊

  1. Track kidney function trends across routine blood tests to detect early decline before symptoms appear.

  2. Compare your eGFR against age-matched normal ranges to put a single result in context.

  3. Prepare informed questions before a nephrology or primary care appointment.

Questions and Answers

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

An eGFR calculator estimates how much blood your kidneys filter per minute, expressed per 1.73 m² of body surface area, using serum creatinine, age, and sex. It matters because kidney function can fall by 50% or more before any physical symptoms appear. Catching a declining trend early, when eGFR drops from 85 to 70 over two years, gives clinicians and patients time to slow progression through blood pressure control, diet, and medication adjustments, well before dialysis or transplant become necessary.

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

In healthy adults under 40, eGFR typically sits above 100 mL/min/1.73 m². After age 40, kidney filtration capacity declines at roughly 1 mL/min/1.73 m² per year as a normal part of aging. This means a reading of 75 in a healthy 70-year-old carries a very different clinical meaning than the same number in a 35-year-old. Values above 90 are classified as normal regardless of age; values between 60 and 89 may be age-appropriate or may warrant monitoring depending on whether other markers of kidney damage are present.

What does a low eGFR result mean?

An eGFR consistently below 60 mL/min/1.73 m² on two measurements at least 90 days apart meets the NKF definition of Chronic Kidney Disease (CKD). At this level, waste products such as urea and creatinine accumulate faster than the kidneys can clear them. Values below 30 indicate severely reduced function requiring close specialist supervision, and values below 15 typically signal kidney failure, at which point dialysis or transplant evaluation becomes necessary.

Is the CKD-EPI formula accurate for everyone?

The 2021 CKD-EPI creatinine equation is validated for adults aged 18 and older across diverse populations and performs well for the majority of patients. It is less reliable in several specific groups: pregnant women (where GFR physiology changes substantially), children and adolescents (who use age-specific pediatric formulas), and individuals with atypical muscle mass such as bodybuilders or patients with severe muscle-wasting conditions, because serum creatinine reflects muscle turnover as well as kidney clearance. In these cases, clinicians often add a cystatin C measurement for a more complete picture.

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 \(\kappa\) is 0.7 for females and 0.9 for males, and \(\alpha\) is -0.241 for females and -0.302 for males. This race-free version was jointly endorsed by the NKF and ASN in 2021 after evidence showed the previous race coefficient reduced diagnostic accuracy for Black patients. It remains the recommended standard in nephrology guidelines as of 2026.

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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.