eGFR Calculator
Estimated glomerular filtration rate (eGFR) is the primary number nephrology uses to stage kidney function. The 2021 CKD-EPI equation removed the race coefficient that the 2009 version used; major societies (NKF, ASN) now recommend the race-free version. This calculator applies the 2021 formula to serum creatinine, age and sex and reports the result with CKD stage interpretation.
How to calculate eGFR
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1
Enter serum creatinine
In mg/dL (US) or micromol/L (most of the world). The tool converts automatically.
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2
Enter age
Full years. The formula is validated for adults 18 and older.
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3
Select sex
Male or female. The equation has sex-specific coefficients.
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4
Read eGFR and CKD stage
Result in mL/min/1.73 m^2, with CKD stage G1-G5 interpretation.
The CKD-EPI 2021 formula (race-free)
eGFR = 142 * min(Scr/kappa, 1)^alpha * max(Scr/kappa, 1)^(-1.200) * 0.9938^age * (1.012 if female)
Where Scr is serum creatinine in mg/dL, and:
- Female: kappa = 0.7, alpha = -0.241
- Male: kappa = 0.9, alpha = -0.302
The reporting unit is mL/min per 1.73 m^2 of body surface area.
CKD staging
| Stage | eGFR (mL/min/1.73 m^2) | Description |
|---|---|---|
| G1 | >= 90 | Normal or high (requires evidence of kidney damage) |
| G2 | 60-89 | Mildly decreased |
| G3a | 45-59 | Mild to moderate decrease |
| G3b | 30-44 | Moderate to severe decrease |
| G4 | 15-29 | Severely decreased |
| G5 | < 15 | Kidney failure |
CKD diagnosis also requires albuminuria or structural abnormalities for stages G1-G2; eGFR alone is not sufficient at those levels.
Why the 2021 update removed race
The 2009 CKD-EPI included a coefficient that increased eGFR for patients identified as Black. Mounting evidence showed this overestimated kidney function in Black patients and contributed to delayed referral for transplant and dialysis. The 2021 refit used a larger, more diverse dataset and produced a single equation without a race term. NKF, ASN and major laboratory societies endorsed the 2021 version for all patients.
Limitations of eGFR
- Not accurate in acute kidney injury. The formula assumes steady-state creatinine; rapidly changing creatinine gives misleading eGFR.
- Affected by muscle mass. Very muscular patients have higher baseline creatinine and may appear to have lower eGFR than reality. Cystatin C-based equations are more accurate in these cases.
- Less accurate above 60. The formula was calibrated in CKD populations; in healthy people the reported eGFR is capped around 120-130 regardless of true function.
- Pregnancy changes kidney physiology; do not apply this formula.
- Children need pediatric-specific equations (Schwartz or newer variants).
Interpreting a single value
A single eGFR is a snapshot. CKD diagnosis requires chronicity: eGFR < 60 for at least 3 months, or markers of kidney damage. A borderline reading should be repeated and confirmed before staging.
Frequently Asked Questions
Labs in transition still report both the 2009 (with race coefficient) and 2021 (race-free) results. Going forward, most labs will report only the 2021 value. If your lab shows only one, check the method footnote to confirm which formula was used.
It is validated up to around 85. Above that, all creatinine-based formulas lose precision because muscle mass declines dramatically. Cystatin C-based eGFR is preferred for frail elderly patients when available.
Cystatin C is a protein cleared by kidneys that is less affected by muscle mass. The 2021 CKD-EPI cystatin equation (and the combined creatinine-cystatin equation) are more accurate in certain patient groups and are increasingly ordered when precision matters.
No. Creatinine, age and sex are used in the browser to compute eGFR. No identifiable information is captured or stored.