CKD eGFR Calculator (CKD-EPI 2021)
Estimate kidney function using age, sex, and serum creatinine. You can also add urine albumin-creatinine ratio (ACR) for a more complete CKD risk view.
What this chronic kidney disease calculator does
This calculator estimates eGFR (estimated glomerular filtration rate) using the CKD-EPI 2021 creatinine equation. eGFR is a standard measure clinicians use to assess kidney filtration function. Lower values generally indicate reduced kidney function.
When available, adding urine ACR helps classify albuminuria and gives better context for CKD risk. Kidney care decisions are best made using both filtration (G category) and albuminuria (A category).
How to use the calculator
- Enter age in years.
- Select sex at birth, because equation coefficients differ.
- Enter serum creatinine and the correct unit (mg/dL or µmol/L).
- Optionally add urine ACR in mg/g.
- Click Calculate to view eGFR, stage category, and interpretation.
Understanding CKD G categories (by eGFR)
G1 to G5 overview
- G1: eGFR ≥ 90 (normal/high filtration range)
- G2: 60–89 (mildly decreased)
- G3a: 45–59 (mild to moderate decrease)
- G3b: 30–44 (moderate to severe decrease)
- G4: 15–29 (severely decreased)
- G5: < 15 (kidney failure range)
Important: G1 or G2 alone does not confirm CKD unless other markers of kidney damage are present (such as persistent albuminuria, structural kidney abnormalities, or urine sediment abnormalities).
Understanding albuminuria A categories (by urine ACR)
- A1: < 30 mg/g (normal to mildly increased)
- A2: 30–300 mg/g (moderately increased)
- A3: > 300 mg/g (severely increased)
Albumin in the urine can indicate kidney damage even when eGFR is near normal. That is why combining G and A categories is clinically useful.
How CKD is diagnosed in real practice
Clinicians generally diagnose CKD when abnormalities of kidney structure or function are present for at least 3 months. A single lab value is helpful but not enough by itself for a definitive diagnosis. Your clinician may repeat blood and urine tests, review blood pressure and diabetes status, and order additional imaging or labs.
Common risk factors
- Diabetes
- High blood pressure
- Cardiovascular disease
- Family history of kidney disease
- Older age
- Long-term NSAID use in susceptible individuals
When to seek medical advice promptly
- eGFR consistently below 60
- Urine ACR repeatedly 30 mg/g or higher
- Rapid decline in kidney function over time
- Swelling, foamy urine, blood in urine, or uncontrolled blood pressure
If results are abnormal, discuss them with your primary care clinician or a nephrologist. Early detection can slow progression and reduce complications.
Limitations of online kidney calculators
No calculator replaces clinical judgment. eGFR estimates can be influenced by muscle mass, diet, acute illness, medications, pregnancy, and lab variability. Some individuals need cystatin C testing or measured clearance studies for better precision.