GFR Calculator
Calculate your estimated Glomerular Filtration Rate (eGFR) to assess kidney function using clinically validated equations.
About This Calculator
How to Use
- Enter your age in years
- Select your biological sex
- Enter your serum creatinine level from blood test
- Select the unit (mg/dL or µmol/L)
- Click Calculate to see your eGFR and CKD stage
📚 Understanding GFR
Glomerular Filtration Rate (GFR) measures the volume of fluid filtered by the kidneys per minute. It's the best overall indicator of kidney function and is used to stage chronic kidney disease (CKD).
GFR naturally declines with age—about 1 mL/min/year after age 40. A normal GFR is typically above 90 mL/min/1.73m² in healthy adults, though values of 60-89 without other signs of kidney damage may be normal in older adults.
Note: eGFR equations are validated for adults with stable kidney function. They may be less accurate in certain populations including those with extreme body size, muscle mass, or acute kidney injury.
🧮 eGFR Equations
eGFR = 142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^-1.200 × 0.9938^age × (1.012 if female)
eGFR = 175 × Scr^-1.154 × age^-0.203 × (0.742 if female)
📊 CKD Stages
| Stage | GFR | Description |
|---|---|---|
| Stage 1 | ≥90 | Normal or high (with kidney damage) |
| Stage 2 | 60–89 | Mildly decreased |
| Stage 3a | 45–59 | Mild to moderate decrease |
| Stage 3b | 30–44 | Moderate to severe decrease |
| Stage 4 | 15–29 | Severely decreased |
| Stage 5 | <15 | Kidney failure (ESKD) |
💡 Practical Use Cases
- Kidney Health Monitoring: Track kidney function over time
- Drug Dosing: Many medications require dose adjustment based on GFR
- CKD Staging: Determine the stage of chronic kidney disease
- Pre-surgical Assessment: Evaluate kidney function before procedures
- Diabetes Management: Monitor for diabetic nephropathy
- Contrast Safety: Assess risk before CT with contrast dye
❓ Frequently Asked Questions
What is the difference between CKD-EPI and MDRD?
CKD-EPI 2021 is the newer, recommended equation that is more accurate, especially at higher GFR values. It no longer includes race as a variable. MDRD tends to underestimate GFR in people with normal or near-normal kidney function.
What is a normal GFR?
A normal GFR is typically above 90 mL/min/1.73m². However, GFR naturally declines with age. Values of 60-89 may be normal in older adults without other signs of kidney damage.
Why does my lab report show a different eGFR?
Labs may use different equations or creatinine assays. Some labs still use older equations. The CKD-EPI 2021 equation used here is the current standard recommended by KDIGO guidelines.
Can I improve my GFR?
While you can't reverse kidney damage, you can slow progression by controlling blood pressure, managing diabetes, avoiding nephrotoxic drugs, staying hydrated, and maintaining a healthy lifestyle. Consult a nephrologist for personalized advice.