CKD-EPI 2021 Equation Explained
The race-free standard for estimating eGFR.
How the race-free CKD-EPI 2021 creatinine equation estimates eGFR and why it replaced the 2009 version.
Medically reviewed by Dr. Rishi Kumar Kafle, MBBS, MD, FASN. Last reviewed October 2026.
The CKD-EPI 2021 creatinine equation estimates eGFR in mL/min/1.73m² from age, sex, and serum creatinine. The full form is 142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^−1.200 × 0.9938^age × (1.012 if female), where κ = 0.7 for female and 0.9 for male patients and α = −0.241 for female and −0.302 for male patients. The equation has no race coefficient.
Every Coefficient Defined
The CKD-EPI equation looks complex because it uses a two-part spline that bends at Scr/κ = 1, so one formula fits the whole range of kidney function. The table below gives each term, its value and its role.
| Term | Value | Role |
|---|---|---|
| Scaling constant | 142 | anchors the result to mL/min/1.73m² |
| κ (kappa) | 0.7 female / 0.9 male | rescales serum creatinine by sex |
| α (alpha) | −0.241 female / −0.302 male | exponent below the Scr/κ = 1 hinge |
| Upper exponent | −1.200 | applied to max(Scr/κ, 1), above the hinge |
| Age term | 0.9938^age | eGFR falls ~0.6% per year of age |
| Female factor | × 1.012 | small upward adjustment for women |
The min/max construction means that for a low creatinine (Scr/κ < 1) the α exponent dominates, while for a high creatinine (Scr/κ > 1) the steeper −1.200 exponent applies. Use the creatinine unit converter to reach mg/dL if your lab reports µmol/L.
A Worked Example
Take a 55-year-old woman with a serum creatinine of 0.9 mg/dL. Here κ = 0.7, so Scr/κ = 0.9 ÷ 0.7 ≈ 1.29. Because that is above 1, the −1.200 exponent applies: 1.29^−1.200 ≈ 0.745. The age term is 0.9938^55 ≈ 0.711, and the female factor is 1.012. Multiplying 142 × 0.745 × 0.711 × 1.012 gives an eGFR of about 76 mL/min/1.73m²: GFR category G2 (mildly decreased). Without signs of kidney damage, such as albuminuria, G2 alone does not meet the definition of CKD.
Why the Race Coefficient Was Removed
The earlier 2009 equation multiplied results for Black patients by a separate factor. In 2021 a joint NKF-ASN task force introduced a race-free equation for all adults, because race is a social rather than biological category and the coefficient could delay diagnosis or transplant referral. This site uses the 2021 equation by default for every adult eGFR estimate.
History: From 2009 to 2021
The CKD-EPI collaboration first published a creatinine equation in 2009 that improved on MDRD, especially at near-normal GFR, but it retained a Black-race multiplier. Over the following decade, evidence accumulated that the race term lacked a biological basis and could underestimate kidney disease severity in Black patients. In 2021 the joint NKF-ASN task force re-fit the equation without race, and that is the version this site uses. The 2021 equation slightly changes the coefficients but keeps the same two-part spline structure, so the result is read the same way: it remains an eGFR in mL/min/1.73m² for staging.
How to Read the Result
A CKD-EPI result maps directly to the KDIGO CKD categories. An eGFR of 90 or above is G1 (normal or high), 60-89 is G2 (mildly reduced), 45-59 is G3a, 30-44 is G3b, 15-29 is G4, and below 15 is G5 (kidney failure). A single eGFR is not a diagnosis on its own: staging also depends on albuminuria and on the value being stable over at least three months. See CKD stages for how the categories combine.
Strengths and Limitations
CKD-EPI 2021 is the most accurate routine creatinine-based equation at near-normal GFR, where MDRD struggled, and it is race-free. Like every creatinine equation, it still assumes average muscle mass and a steady state. It is therefore less reliable in people with very high or very low muscle (athletes, amputees, the frail), in acute kidney injury, in pregnancy, or at the extremes of body size. When creatinine alone is unreliable, a cystatin C-based equation, which does not depend on muscle mass, can be paired with it to refine the estimate. For children, the adult equation does not apply; use the bedside Schwartz equation instead.
CKD-EPI vs Other Equations
CKD-EPI is more accurate at near-normal GFR than MDRD. It is the standard for CKD staging, while Cockcroft-Gault remains the choice for drug dosing. Compare them on CrCl vs eGFR and MDRD vs CKD-EPI.