GFR Calculator
Calculate your Glomerular Filtration Rate to assess kidney function
Gender
Age
years
Race/Ethnicity
Serum Creatinine
mg/dL
Creatinine Units
Additional Factors
Your Glomerular Filtration Rate Results
Estimated kidney function based on your lab values
90
Normal Kidney Function
Your estimated GFR indicates normal kidney function
Kidney Disease Staging
Stage 1
≥90
Stage 2
60-89
Stage 3a
45-59
Stage 3b
30-44
Stage 4
15-29
Stage 5
<15
GFR Interpretation
90
Estimated GFR (mL/min)
1
Kidney Disease Stage
100%
Relative Kidney Function
Yearly
Recommended Follow-up
Chronic Kidney Disease Stages
| Stage | GFR Range (mL/min) | Description | Kidney Function | Actions |
|---|---|---|---|---|
| 1 | ≥90 | Kidney damage with normal GFR | Normal or High | Treat underlying condition, monitor |
| 2 | 60-89 | Kidney damage with mild ↓ GFR | Mildly Decreased | Estimate progression, control risk factors |
| 3a | 45-59 | Moderate ↓ GFR | Mild to Moderate Loss | Evaluate and treat complications |
| 3b | 30-44 | Moderate to Severe ↓ GFR | Moderate to Severe Loss | Prepare for renal replacement |
| 4 | 15-29 | Severe ↓ GFR | Severe Loss | Prepare for kidney failure treatment |
| 5 | <15 | Kidney Failure | Kidney Failure | Dialysis or transplant needed |
About Glomerular Filtration Rate (GFR)
Glomerular Filtration Rate (GFR) is the best test 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.
GFR Calculation Formula
This calculator uses the CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) equation, which is the current standard for estimating GFR:
For women (non-African American):
- If serum creatinine ≤ 0.7 mg/dL: GFR = 144 × (creatinine/0.7)^(-0.329) × (0.993)^age
- If serum creatinine > 0.7 mg/dL: GFR = 144 × (creatinine/0.7)^(-1.209) × (0.993)^age
For men (non-African American):
- If serum creatinine ≤ 0.9 mg/dL: GFR = 141 × (creatinine/0.9)^(-0.411) × (0.993)^age
- If serum creatinine > 0.9 mg/dL: GFR = 141 × (creatinine/0.9)^(-1.209) × (0.993)^age
For African Americans: Multiply the result by 1.159
Normal GFR Values
| Age Group | Average GFR | Normal Range | Notes |
|---|---|---|---|
| 20-29 years | 116 mL/min | 88-146 mL/min | Peak kidney function |
| 30-39 years | 107 mL/min | 82-140 mL/min | Slight decline begins |
| 40-49 years | 99 mL/min | 75-133 mL/min | Gradual age-related decline |
| 50-59 years | 93 mL/min | 68-126 mL/min | Continued decline |
| 60-69 years | 85 mL/min | 60-119 mL/min | Significant age effect |
| 70+ years | 75 mL/min | 50-105 mL/min | Normal aging decline |
Factors Affecting GFR
- Age: GFR naturally declines by about 1 mL/min/year after age 40
- Gender: Men typically have higher GFR than women due to larger body size
- Race/Ethnicity: African Americans typically have higher muscle mass and creatinine production
- Body Size: Larger individuals have higher GFR
- Pregnancy: GFR increases by 40-50% during pregnancy
- Diet: High protein intake can temporarily increase GFR
- Medications: Some drugs affect kidney function
Limitations of eGFR Calculation
- eGFR is an estimate - not as accurate as measured GFR (mGFR)
- Less accurate at higher GFR levels (>60 mL/min)
- May be inaccurate in certain populations (children, elderly, amputees, bodybuilders)
- Does not account for acute kidney injury
- Affected by variations in creatinine production (diet, muscle mass)
- Not validated in all ethnic groups
When to See a Doctor
- eGFR < 60 mL/min for 3 months or more
- Rapid decline in eGFR (≥5 mL/min/year)
- Presence of protein or blood in urine
- Family history of kidney disease
- Diabetes, hypertension, or cardiovascular disease
- Unexplained fatigue, swelling, or changes in urination
Important Medical Disclaimer
- This calculator provides estimates only and is not a medical diagnosis
- eGFR results should be interpreted by a healthcare professional
- Actual kidney function assessment requires comprehensive medical evaluation
- Never adjust medications or treatment based on calculator results alone
- Consult with a nephrologist or primary care physician for proper kidney function assessment
- Regular monitoring with a healthcare provider is essential for accurate kidney health management