eGFR Calculator (NKF-style, CKD-EPI 2021)
Estimate kidney function using serum creatinine, age, and sex.
What this National Kidney Foundation calculator does
This page estimates eGFR (estimated glomerular filtration rate), a key number used to assess kidney function. It uses the CKD-EPI 2021 creatinine equation, which is commonly used in modern clinical reporting and does not include race. Results are shown in mL/min/1.73m², along with a CKD G-stage interpretation.
How to use the calculator
- Enter your serum creatinine value from your lab report.
- Select the correct creatinine unit (mg/dL or µmol/L).
- Enter your age.
- Select sex.
- (Optional) Add urine albumin-creatinine ratio (ACR) to get albuminuria category and risk context.
Understanding your result
eGFR staging (G categories)
- G1: 90 or higher
- G2: 60 to 89
- G3a: 45 to 59
- G3b: 30 to 44
- G4: 15 to 29
- G5: under 15
Albuminuria (A categories, optional)
- A1: under 30 mg/g
- A2: 30 to 300 mg/g
- A3: over 300 mg/g
Kidney risk is best interpreted by combining both G category (eGFR) and A category (ACR). Trends over time are usually more useful than one single measurement.
Why eGFR can change
eGFR depends on creatinine, and creatinine can vary with hydration, muscle mass, diet, medications, and lab methods. A temporary drop does not always mean chronic kidney disease. Clinicians usually interpret kidney function with:
- repeat lab values over at least 3 months,
- urine testing (including albumin),
- blood pressure and diabetes status,
- medication review, and
- clinical context (acute illness vs. stable outpatient state).
Who should use caution with this calculator
Creatinine-based equations may be less accurate in certain situations, such as pregnancy, acute kidney injury, severe malnutrition, unusual muscle mass, or pediatric patients. If these apply to you, ask your provider whether cystatin C or measured GFR is more appropriate.
Practical next steps if your eGFR is low
- Repeat testing as advised by your clinician.
- Check urine albumin (ACR) if not already done.
- Control blood pressure, blood sugar, and cardiovascular risk factors.
- Review over-the-counter drugs (especially NSAIDs) with a professional.
- Discuss kidney-protective therapies if clinically appropriate.