GFR Calculator – Check Kidney Function Instantly
The GFR Calculator helps estimate your glomerular filtration rate, which indicates how well your kidneys are functioning. It is widely used in diagnosing and monitoring chronic kidney disease (CKD). The tool uses the CKD-EPI or MDRD equation based on your serum creatinine, age, sex, and race.
How to Use the GFR Calculator
Enter the following:
- Age (in years)
- Gender (male or female)
- Serum creatinine level (mg/dL or µmol/L)
- Race (Black or non-Black)
The calculator estimates your eGFR (estimated GFR) using standard medical equations.
GFR Formula (CKD-EPI Equation)
eGFR = 141 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^−1.209 × 0.993^Age × (1.018 if female) × (1.159 if Black)
Where:
- Scr = serum creatinine
- κ = 0.7 for females, 0.9 for males
- α = −0.329 for females, −0.411 for males
Example
Age: 45
Gender: Male
Creatinine: 1.2 mg/dL
Race: Non-Black
→ eGFR ≈ 78 mL/min/1.73 m² (based on CKD-EPI formula)
GFR & Kidney Function Stages
- GFR ≥ 90: Normal
- GFR 60–89: Mildly decreased
- GFR 30–59: Moderate kidney disease
- GFR 15–29: Severe kidney disease
- GFR < 15: Kidney failure (Stage 5 CKD)
Common Use Cases
- Monitoring kidney function over time
- Evaluating for chronic kidney disease (CKD)
- Adjusting medication dosage in renal patients
- Pre-diagnosis screening in high-risk patients (diabetics, hypertensives)
Why Use a GFR Calculator?
Accurate GFR estimates help detect early signs of kidney damage, allowing timely intervention and treatment. It’s a standard test in nephrology and internal medicine.
Frequently Asked Questions (FAQs)
What is a normal GFR?
Above 90 is considered normal kidney function if there are no other signs of disease.
Does GFR change with age?
Yes, GFR naturally declines as you get older, even without kidney disease.
How is serum creatinine measured?
Through a simple blood test. Accurate creatinine is essential for reliable GFR estimates.
Is race still used in GFR calculations?
Some guidelines have removed race; however, older formulas like CKD-EPI still use it optionally.
What should I do if my GFR is low?
Consult a nephrologist. Early intervention, hydration, and diet can help manage kidney function.
Related tools: BMR Calculator.