GFR Calculator (CKD-EPI 2021)
Estimate Glomerular Filtration Rate to assess kidney function.
Estimated GFR
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mL/min/1.73 m²
What is GFR and Why Does it Matter?
Glomerular Filtration Rate (GFR) is the best overall index of kidney function. It describes the flow rate of filtered fluid through the kidney. A high GFR indicates healthy kidneys, while a lower GFR suggests that the kidneys are not filtering waste products from the blood as efficiently as they should.
How the CKD-EPI (2021) Formula Works
This calculator uses the CKD-EPI Creatinine Equation (2021), which is the current clinical standard. Unlike older formulas, the 2021 version does not include a race-based coefficient, providing a more equitable assessment of kidney health across diverse populations.
The mathematical logic behind the calculation is based on your serum creatinine level, age, and biological sex:
- Serum Creatinine: A waste product from muscle breakdown. Higher levels often indicate decreased kidney filtration.
- Age: Kidney function naturally declines with age.
- Sex: Men generally have higher muscle mass, resulting in higher baseline creatinine levels than women.
Interpreting Your GFR Results
| GFR Level | Stage | Meaning |
|---|---|---|
| 90 or higher | 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 |
| Less than 15 | Stage 5 | Kidney failure (ESRD) |
Example Calculation
If a 50-year-old male has a serum creatinine of 1.2 mg/dL:
- Input: 1.2 mg/dL, 50 Years, Male.
- Logic: The CKD-EPI formula applies specific constants for males and scales the result based on the creatinine value relative to 0.9 mg/dL.
- Result: Approximately 76 mL/min/1.73 m², indicating Stage 2 (mildly decreased function).
Note: This calculator is for educational purposes. Always consult a medical professional for diagnosis and treatment.