eGFR Calculator (CKD-EPI 2021)

The CKD-EPI 2021 Equation

This calculator uses the race-free CKD-EPI 2021 creatinine equation, the version now recommended by the NKF-ASN task force and adopted by laboratories and guidelines in the United States and Europe:

• eGFR = 142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^−1.200 × 0.9938^age × 1.012 (if female)
• κ = 0.7 (female) or 0.9 (male); α = −0.241 (female) or −0.302 (male)
• Scr is serum creatinine in mg/dL; divide µmol/L by 88.4 to convert

Earlier equations included a race coefficient. It was removed because race is a social rather than biological construct, and because the adjustment contributed to delays in referral and transplant listing for Black patients. The 2021 equation estimates slightly lower eGFR in people who would previously have received the adjustment.

KDIGO eGFR Categories

• G1 — 90 or above (normal or high)
• G2 — 60 to 89 (mildly reduced)
• G3a — 45 to 59 (mild to moderately reduced)
• G3b — 30 to 44 (moderately to severely reduced)
• G4 — 15 to 29 (severely reduced)
• G5 — below 15 (kidney failure)

An eGFR category on its own is not a diagnosis of chronic kidney disease. CKD requires abnormalities of kidney structure or function present for more than three months, which is why staging pairs the eGFR category with an albuminuria category (A1, A2 or A3) from a urine albumin-to-creatinine ratio.

When eGFR Is Least Reliable

• Creatinine-based equations assume stable muscle mass. Amputation, paralysis, severe sarcopenia, cachexia and bodybuilding all shift the estimate. Cystatin C–based equations are more accurate in these groups.
• Non-steady state. In acute kidney injury, or within days of a large change in kidney function, creatinine lags behind the true GFR.
• Drugs that block tubular secretion (trimethoprim, cimetidine) raise creatinine without lowering GFR, so the estimate falls falsely.
• Extremes of body size and pregnancy both reduce accuracy.

Frequently Asked Questions