GFR Calculator (CKD-EPI 2021)
Estimated GFR: — mL/min/1.73m²
Kidney Function Status: —
Understanding Your GFR Result
Glomerular Filtration Rate (GFR) is the best way to measure your level of kidney function and determine your stage of kidney disease. It estimates how much blood passes through the glomeruli (tiny filters in the kidneys) each minute. This calculator uses the CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) 2021 equation, which is the current clinical standard as it does not include race-based variables.
CKD Stages and Interpretations
| GFR Level | Stage | Interpretation |
|---|---|---|
| 90 or above | Stage 1 | Normal kidney function |
| 60 – 89 | Stage 2 | Mildly decreased function |
| 45 – 59 | Stage 3a | Mild-to-moderate decrease |
| 30 – 44 | Stage 3b | Moderate-to-severe decrease |
| 15 – 29 | Stage 4 | Severely decreased function |
| Below 15 | Stage 5 | Kidney failure (ESRD) |
Practical Example of GFR Calculation
Suppose a 55-year-old male has a serum creatinine level of 1.4 mg/dL. Using the CKD-EPI formula:
- Age: 55
- Creatinine: 1.4 mg/dL
- Sex: Male
- Calculation: The formula processes these variables with mathematical constants to account for muscle mass and metabolism.
- Result: Approximately 60 mL/min/1.73m².
- Meaning: This individual would be at the borderline of Stage 2 and Stage 3a kidney disease.
Why is Serum Creatinine Important?
Creatinine is a waste product that comes from the normal wear and tear on muscles of the body. Healthy kidneys filter creatinine from the blood. When kidney function slows down, creatinine levels rise. However, because creatinine levels vary based on muscle mass, age, and sex, the GFR calculation provides a more accurate picture of kidney health than looking at creatinine alone.
Disclaimer: This calculator is for educational purposes only. Results should be interpreted by a healthcare professional. Clinical decisions should not be based solely on this tool.