Estimated GFR (eGFR) Calculator
Utilizing the CKD-EPI 2021 Race-Neutral Formula
Contents
Input Values
Calculated Result
Estimated GFR is:
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mL/min/1.73m²
Understanding Glomerular Filtration Rate (GFR) and CKD Stages
The Glomerular Filtration Rate (GFR) is universally recognized as the best index of overall kidney function. It measures how much blood passes through the tiny filters in the kidneys, called glomeruli, each minute. [Image of a kidney nephron showing the glomerulus filtering blood] A GFR result helps healthcare providers determine if kidney disease is present, and if so, what stage it is in. For a young, healthy adult, the GFR is typically around 120 mL/min/1.73m². As a person ages, a natural decline in GFR is expected.
The latest methodology for estimating GFR is the CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) 2021 equation. This version was developed to eliminate the race variable that was present in the 2009 formula, promoting greater equity in clinical care. The exclusion of the race variable means that the GFR estimate is based solely on measured serum creatinine, age, and sex. This shift ensures a standardized assessment for all patients, avoiding inherent biases associated with historical race-based adjustments.
The CKD (Chronic Kidney Disease) Staging System
Chronic Kidney Disease (CKD) is staged based primarily on the GFR value. The lower the number, the more impaired the kidney function. These stages guide treatment decisions and monitoring frequency.
| Stage | GFR (mL/min/1.73m²) | Interpretation |
|---|---|---|
| G1 (Normal/High) | ≥ 90 | Normal kidney function, possibly with other evidence of kidney damage (e.g., protein in urine). |
| G2 (Mildly Decreased) | 60 – 89 | Mild reduction in kidney function, often with associated kidney damage. |
| G3a (Mild-to-Moderate) | 45 – 59 | Mild-to-moderate reduction in kidney function. |
| G3b (Moderate-to-Severe) | 30 – 44 | Moderate-to-severe reduction in kidney function. |
| G4 (Severely Decreased) | 15 – 29 | Severe reduction in kidney function, preparation for kidney replacement therapy is often necessary. |
| G5 (Kidney Failure) | < 15 | Established kidney failure, requiring dialysis or transplant. |
The CKD-EPI 2021 Formula
The GFR is mathematically calculated based on the following general structure, where the coefficients (k) and exponents (a) change based on the patient’s sex.
eGFR = 142 x min(Cr/k, 1)^a x max(Cr/k, 1)^-1.200 x 0.9938^Age x (Sex Factor)
Where:
- Cr is serum creatinine in mg/dL.
- k is 0.7 for females and 0.9 for males.
- a is -0.241 for females and -0.302 for males.
- The Sex Factor is 1.012 for females and 1.0 for males.
Internal Linking: For tools on other physiological calculations, you may find our Reach Estimation Utility or Global Time Calculator helpful.