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eGFR CKD-EPI 2021 Calculator

Enter serum creatinine, age, and sex to estimate eGFR.

How it is calculated

Inputs are serum creatinine Scr in mg/dL, age in years and sex (male or female). With kappa = 0.9 and alpha = −0.302 for men, or kappa = 0.7 and alpha = −0.241 for women, the tool computes eGFR = 142 × min(Scr/κ, 1)α × max(Scr/κ, 1)−1.200 × 0.9938age, multiplied by 1.012 for women. The result is rounded to a whole number in mL/min/1.73 m² and mapped to a stage: G1 at 90 or above, G2 60–89, G3a 45–59, G3b 30–44, G4 15–29, G5 below 15. Creatinine and age must be above zero. There is no race term. The stage is based on the number alone; real CKD staging also needs albuminuria and repeat tests over time. Educational use only, not medical advice.

Worked example

A 60-year-old man with creatinine 1.1 mg/dL. Scr/κ = 1.1 ÷ 0.9 = 1.222, which is above 1, so only the max term is active: 1.222−1.2 = 0.786. Age factor: 0.993860 = 0.689. eGFR = 142 × 0.786 × 0.689 = 76.9, shown as 77 mL/min/1.73m², stage G2 (mildly decreased, 60–89).

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Common mistakes

  • Entering creatinine in µmol/L (for example 97) instead of mg/dL (1.1); the equation then returns a tiny eGFR. Divide µmol/L by 88.4 first.
  • Choosing the wrong sex, which changes both constants; for the same creatinine and age the female value differs noticeably from the male one.
  • Reading one result as a diagnosis; staging relies on repeated results over time and other tests, not a single number.
  • Using the formula for children, in pregnancy, or for people with unusual muscle mass or diet, where creatinine-based estimates are less reliable.
  • Comparing against an older report that used the 2009 equation with a race coefficient; the numbers are not directly interchangeable.

Sources

About this calculator

eGFR (estimated glomerular filtration rate) is the primary lab-based measure of kidney function, and the 2021 CKD-EPI creatinine equation is the current standard formula recommended by the National Kidney Foundation and American Society of Nephrology to calculate it from a routine blood test. It replaced the 2009 CKD-EPI equation specifically to remove the race coefficient that had been applied for Black patients, after evidence showed race-based adjustment was not a reliable biological proxy and could delay care; the 2021 version uses only serum creatinine, age, and sex, applying different constants (kappa, alpha) and a minimum/maximum term structure depending on whether creatinine falls above or below a sex-specific threshold.

The resulting eGFR, in mL/min/1.73m², is then mapped to a CKD stage under KDIGO guidelines — G1 (normal, eGFR 90+) through G5 (kidney failure, below 15) — which nephrologists and primary care physicians use to stage chronic kidney disease, guide referral timing, and adjust medication dosing. This tool is for education only and does not replace a clinical lab result or physician interpretation.

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Comments (1)

  • Editorial team

    The field expects creatinine in mg/dL. Many labs outside the United States report micromoles per litre instead, and dividing that value by 88.4 gives mg/dL, so 100 umol/L is about 1.13 mg/dL. Entering the raw micromole figure would produce a very low eGFR and a wrong stage. Creatinine also depends on muscle mass and varies with the lab, so one number is a starting point for a conversation with your clinician. Which units does your lab report use?

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