eGFR Calculator (CKD-EPI 2021)

Estimate glomerular filtration rate using the 2021 CKD-EPI creatinine equation — the race-free formula now recommended in the United States — and map the result to a CKD stage.

🧪 Lab Value📐 eGFR = 142 × min(Scr/κ,1)^α × max(Scr/κ,1)^−1.200 × 0.9938^age × 1.012 [female]🏥 Health
Sex
Age (years)
Serum creatinine (mg/dL)
Please enter valid values.

Formula & Reference

VariableSymbolFormulaUnits
eGFR Calculator (CKD-EPI 2021)—eGFR = 142 × min(Scr/κ,1)^α × max(Scr/κ,1)^−1.200 × 0.9938^age × 1.012 [female]mL/min/1.73m²

Step-by-Step Examples

Example 1
Normal Function

48-year-old man, serum creatinine 0.95 mg/dL.

  • Male κ = 0.9, so Scr/κ = 1.056 (above 1)
  • Uses the −1.200 exponent branch
  • Age factor = 0.9938^48
  • eGFR ≈ 99 mL/min/1.73m²
✓ eGFR 99 — stage G1
Example 2
Moderate Reduction

67-year-old woman, serum creatinine 1.4 mg/dL.

  • Female κ = 0.7, so Scr/κ = 2.0
  • Female multiplier 1.012 applied
  • eGFR ≈ 41 mL/min/1.73m²
✓ eGFR 41 — stage G3b
Example 3
Advanced Disease

72-year-old man, serum creatinine 3.6 mg/dL.

  • Scr/κ = 4.0, well above 1
  • Steep −1.200 exponent drives the estimate down
  • eGFR ≈ 17 mL/min/1.73m²
✓ eGFR 17 — stage G4

Real-World Applications

🧪
Routine Laboratory Reporting
Most laboratories now report eGFR automatically alongside every serum creatinine result, using the 2021 race-free equation in the US.
💊
Medication Safety
Many drugs require dose review or avoidance below specific eGFR thresholds, making the estimate a routine prescribing checkpoint.
🏥
Nephrology Referral
eGFR combined with albuminuria determines who warrants specialist kidney care under KDIGO guidance.
📈
Disease Monitoring
Tracking eGFR trajectory over years reveals progression rate far better than any single measurement.

Common Mistakes to Avoid

⚠️
Reading a single low eGFR as chronic kidney disease

CKD requires abnormality persisting beyond three months. A single low value may reflect acute kidney injury, dehydration, or recent high protein intake.

⚠️
Applying eGFR during unstable kidney function

The equation assumes steady-state creatinine. In rapidly changing acute kidney injury, eGFR lags well behind true filtration and misleads.

⚠️
Forgetting that muscle mass distorts creatinine

Very muscular people, amputees, people with cirrhosis, and those with low muscle mass all have creatinine values that misrepresent filtration. Cystatin C-based estimates are more reliable in these situations.

Frequently Asked Questions

What changed in the 2021 CKD-EPI equation? ▾
The race coefficient was removed. The previous equation applied a multiplier for Black patients, which was recognized as scientifically unjustified and potentially harmful to care access.
What is a normal eGFR? ▾
Roughly 90 mL/min/1.73m² or above in healthy adults, though eGFR declines gradually with age even in the absence of kidney disease.
Does a low eGFR always mean kidney disease? ▾
No. Transient reductions occur with dehydration, certain medications, and acute illness. Diagnosis requires abnormality persisting for at least three months.
Should cystatin C be used instead of creatinine? ▾
Current guidance suggests confirming with a cystatin C-based estimate when creatinine-based eGFR may be inaccurate or when the result will drive an important clinical decision.
Why is eGFR indexed to 1.73m²? ▾
To standardise across body sizes. For decisions where absolute clearance matters — certain drug doses, for example — the value should be de-indexed to the patient's actual body surface area.

Related Health Calculators

🧪 Creatinine Clearance🧪 CKD Staging🧪 Urine ACR💊 Renal Dose Adjustment📏 Body Surface Area