eGFR Calculator (CKD-EPI 2021)

Estimate glomerular filtration rate (eGFR) from serum creatinine, age and sex using the race-free 2021 CKD-EPI creatinine equation recommended by the National Kidney Foundation and the American Society of Nephrology.

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Sex
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Medical disclaimer: This calculator is intended for educational and informational purposes and does not replace professional medical advice, diagnosis, laboratory interpretation, or treatment. Laboratory methods and reference intervals vary. Always consult a qualified healthcare professional about your results.

How the eGFR Calculator works

Glomerular filtration rate (GFR) describes how much blood the kidneys filter each minute. Measuring GFR directly is complex, so in routine practice it is estimated from serum creatinine — a waste product cleared by the kidneys — together with age and sex. The result is reported in mL/min/1.73m², i.e. normalized to an average adult body surface area.

eGFR is commonly used to screen for and monitor chronic kidney disease (CKD) and to stage it alongside urine albumin (see the Albumin Creatinine Ratio Calculator).

Required inputs

  • Age (18 years or older — the equation is for adults)
  • Sex
  • Serum creatinine in mg/dL or µmol/L (standardized, IDMS-traceable assay)

Race is not used. The 2021 equation removed the race coefficient used in earlier versions.

Formula used

CKD-EPI 2021 creatinine equation (Inker et al., NEJM 2021):

eGFR = 142 × min(Scr/κ, 1)α × max(Scr/κ, 1)−1.200 × 0.9938Age × 1.012 [if female]
  • Scr = serum creatinine in mg/dL (µmol/L ÷ 88.4)
  • κ = 0.7 (female) or 0.9 (male)
  • α = −0.241 (female) or −0.302 (male)
  • min / max = the smaller / larger of Scr/κ and 1

Worked example

A 50-year-old man with a serum creatinine of 1.0 mg/dL:

  • Scr/κ = 1.0 ÷ 0.9 = 1.111 → min term = 1, max term = 1.111−1.200 = 0.881
  • Age term = 0.993850 = 0.733
  • eGFR = 142 × 1 × 0.881 × 0.733 ≈ 92 mL/min/1.73m²

Interpreting the result

KDIGO groups GFR into categories. They are shown for education only — CKD is defined by kidney abnormalities (reduced GFR and/or markers such as albuminuria) present for more than 3 months.

CategoryeGFR (mL/min/1.73m²)KDIGO description
G1≥ 90Normal or high
G260–89Mildly decreased
G3a45–59Mildly to moderately decreased
G3b30–44Moderately to severely decreased
G415–29Severely decreased
G5< 15Kidney failure

G1 and G2 alone do not indicate CKD unless other markers of kidney damage are present.

Limitations

  • Assumes stable kidney function — not reliable in acute kidney injury or when creatinine is changing quickly.
  • Creatinine depends on muscle mass and diet; results may be less accurate in very muscular or frail people, amputees, people on vegetarian or high-protein diets, or those taking creatine supplements.
  • Not validated in children or in pregnancy.
  • Some medications (e.g. trimethoprim, cimetidine) raise creatinine without changing GFR.
  • When more accuracy is needed, clinicians may use cystatin C–based equations or measured GFR.

Frequently asked questions

eGFR estimates how much blood the kidneys filter per minute, adjusted to a standard body size (mL/min/1.73m²). It is calculated from serum creatinine, age and sex rather than measured directly.

The CKD-EPI 2021 creatinine equation needs serum creatinine, age (18+) and sex. It does not use race or body weight.

No. eGFR (CKD-EPI) is normalized to 1.73m² body surface area, while Cockcroft-Gault creatinine clearance is in mL/min and depends on body weight. They often give different numbers and are used for different purposes.

Hydration, recent meat intake, intense exercise, illness, medications and normal laboratory variation can all shift creatinine — and therefore eGFR — from one test to the next. Trends over time are more informative than a single value.

No. CKD is diagnosed by a clinician based on abnormalities persisting for more than 3 months, usually including urine albumin testing. A single calculated eGFR cannot diagnose CKD.
Medical disclaimer: This calculator is intended for educational and informational purposes and does not replace professional medical advice, diagnosis, laboratory interpretation, or treatment. Laboratory methods and reference intervals vary. Always consult a qualified healthcare professional about your results.