CKD-EPI 2021 Creatinine eGFR Calculator
CKD-EPI 2021 Creatinine eGFR Calculator
Estimate GFR from creatinine, age and sex using the 2021 race-free CKD-EPI equation, the current standard for adults.
CKD-EPI 2021 Creatinine eGFR
Race-free equationMale, age 62, creatinine 1.3 mg/dL
Formula
- κ
- 0.7 in women, 0.9 in men
- α
- −0.241 in women, −0.302 in men
- Scr
- serum creatinine in mg/dL, IDMS-traceable assay
- min / max
- the two-slope structure lets the equation bend at the sex-specific creatinine value κ
- result
- mL/min/1.73 m² — indexed to body surface area, not an absolute clearance
Worked example
Male, age 62, creatinine 1.3 mg/dL
κ = 0.9, α = −0.302, so Scr/κ = 1.3 ÷ 0.9 = 1.444
min(1.444, 1) = 1 · max(1.444, 1) = 1.444
142 × 1 × 1.444^−1.200 × 0.9938^62 = 62 mL/min/1.73 m²
GFR categories
| Category | eGFR | Description |
|---|---|---|
| G1 | ≥ 90 | Normal or high |
| G2 | 60 – 89 | Mildly decreased |
| G3a | 45 – 59 | Mildly to moderately decreased |
| G3b | 30 – 44 | Moderately to severely decreased |
| G4 | 15 – 29 | Severely decreased |
| G5 | < 15 | Kidney failure |
What changed in 2021, and why
The 2009 CKD-EPI equation included a coefficient of 1.159 for Black patients, which raised their estimated GFR by about 16% at the same creatinine. The justification was empirical — average creatinine generation differs between the groups studied — but race is a social category rather than a biological measure of muscle mass, and applying a population coefficient to an individual produced real harm: later referral to nephrology, later transplant listing, and reduced eligibility for donation.
The 2021 refit removed the race term and re-estimated every coefficient on the pooled data. The cost is a modest loss of accuracy at the population level, slightly overestimating GFR in Black adults and underestimating it in others, and the CKD-EPI investigators were explicit that where precision matters the answer is to measure cystatin C rather than to reintroduce race.
Two things about the output are worth holding onto. It is indexed to a body surface area of 1.73 m², so it is a staging tool rather than an absolute clearance — for drug dosing in a very large or very small person, de-index it. And it assumes steady state: in acute kidney injury, where creatinine is still rising, any eGFR equation reports a value from several days ago rather than the kidney’s current function.
Frequently asked questions
What is the CKD-EPI 2021 equation?
The current standard equation for estimating GFR in adults from creatinine, age and sex. It replaced the 2009 version by removing the race coefficient and refitting the remaining terms.
Why was race removed from the eGFR equation?
Race is a social category, not a measure of muscle mass, and applying a population-level coefficient to an individual delayed referral, transplant listing and donation eligibility for Black patients. The 2021 refit removed it.
Should I use creatinine or cystatin C?
Creatinine alone is adequate for most patients. Where the estimate will drive a major decision — transplant listing, chemotherapy dosing, or when muscle mass is atypical — the combined creatinine-cystatin C equation is more accurate and is what guidelines recommend confirming with.
Can eGFR be used in acute kidney injury?
No. Every eGFR equation assumes creatinine is in steady state. While creatinine is rising the equation reports function from several days earlier and substantially overestimates current GFR.
Why is my eGFR reported as over 90 rather than a number?
Many laboratories truncate above 90 because the equation is imprecise in that range. The difference between 95 and 130 is not reliably measurable by creatinine-based estimation.
Related calculators
References
- Inker LA et al. New creatinine- and cystatin C-based equations to estimate GFR without race. N Engl J Med. 2021;385(19):1737–49.
- NIDDK. Estimated glomerular filtration rate equations for adults.
- KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease.