How the CKD-EPI 2021 eGFR Equation Works
eGFR estimates how much blood the kidneys filter each minute, standardised to a body surface area of 1.73 m². The CKD-EPI 2021 creatinine equation is the current race-free standard, recommended by the National Kidney Foundation and the American Society of Nephrology.
eGFR = 142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^-1.200 × 0.9938^age × 1.012 [if female] Here Scr is serum creatinine in mg/dL; κ is 0.7 for females and 0.9 for males; and α is -0.241 for females and -0.302 for males. If your creatinine is in µmol/L, divide by 88.4 to get mg/dL first — or just select µmol/L above. Convert creatinine directly on the creatinine mg/dL to µmol/L calculator.
CKD Stages by eGFR
| Stage | eGFR (mL/min/1.73m²) | Meaning |
|---|---|---|
| G1 | 90 and above | Normal or high (needs kidney damage markers for CKD) |
| G2 | 60–89 | Mildly decreased (needs damage markers for CKD) |
| G3a | 45–59 | Mildly to moderately decreased |
| G3b | 30–44 | Moderately to severely decreased |
| G4 | 15–29 | Severely decreased |
| G5 | Below 15 | Kidney failure |
Stages G1 and G2 are only classed as CKD when there are other markers of kidney damage, such as albuminuria. An eGFR below 60 that persists for three months or more defines CKD on its own.
eGFR vs Creatinine Clearance
eGFR (CKD-EPI) is the standard for staging kidney disease. The older Cockcroft-Gault creatinine clearance is still used for some medication dosing because many drug labels were written against it — use the creatinine clearance calculator for that. Both rely on creatinine, so read them alongside urea/BUN and urine tests.
Worked Example
A 50-year-old man with a creatinine of 0.9 mg/dL: with κ = 0.9 the ratio is 1.0, so the equation gives an eGFR of about 104 mL/min/1.73m² — stage G1, normal.
Frequently Asked Questions
What equation is used?
The race-free CKD-EPI 2021 creatinine equation.
What is a normal eGFR?
90 or above is normal; below 60 for 3+ months defines CKD; below 15 is kidney failure.
Can I use µmol/L creatinine?
Yes — select µmol/L and it is converted by dividing by 88.4.
Why is race removed?
The 2021 update gives a single race-free estimate to reduce diagnostic disparities.
References
- NIDDK — eGFR equations for adults (CKD-EPI 2021).
- National Kidney Foundation — Implementing the CKD-EPI 2021 race-free eGFR calculation.
Conclusion
The CKD-EPI 2021 equation turns creatinine, age and sex into an eGFR and a CKD stage. Enter your values above, then read the result with your clinician alongside creatinine, urea and urine testing — a single estimate is not a diagnosis.