CKD / eGFR Calculator (CKD-EPI 2021)
Use this tool to estimate kidney function (eGFR) from serum creatinine and identify the G category for chronic kidney disease (CKD). You can also add urine ACR to see a rough KDIGO risk level.
| G Category | eGFR (mL/min/1.73m²) | Meaning |
|---|---|---|
| G1 | ≥ 90 | Normal or high (if kidney damage markers present) |
| 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 |
What Is a CKD Calculator?
A CKD calculator estimates kidney function using lab and demographic information. Most commonly, it produces an estimated glomerular filtration rate (eGFR), which is a practical indicator of how well your kidneys filter blood. It does not directly measure kidney filtration, but it is widely used in primary care, nephrology, and hospital settings.
This page uses the CKD-EPI 2021 creatinine equation, which is the race-free version used in many modern clinical systems.
How This CKD Calculator Works
Inputs Used
- Age (adult patients)
- Sex at birth (needed by the equation)
- Serum creatinine (mg/dL or µmol/L)
- Urine ACR (optional, for albuminuria risk grouping)
Outputs You Get
- eGFR value in mL/min/1.73m²
- G category (G1 through G5)
- A category from ACR if provided (A1, A2, A3)
- Approximate KDIGO risk level when both G and A categories are available
How to Interpret Your Result
GFR Categories (G1 to G5)
Lower eGFR generally means lower kidney filtering function. But one value is not enough to diagnose CKD by itself. Persistent abnormalities over time matter.
- G1–G2: Can be normal in many people unless other kidney damage markers are present (protein in urine, structural findings, etc.).
- G3a–G3b: Usually indicates clinically relevant reduction and needs follow-up.
- G4–G5: Severe impairment range; prompt specialist care is often needed.
Albuminuria Categories (A1 to A3)
ACR tells us how much albumin leaks into urine. Albumin leakage can indicate kidney damage even when eGFR is still above 60.
- A1: <30 mg/g (normal to mildly increased)
- A2: 30–300 mg/g (moderately increased)
- A3: >300 mg/g (severely increased)
When a Result Suggests Possible CKD
CKD is typically defined by one of the following, present for at least 3 months:
- eGFR less than 60 mL/min/1.73m², or
- Evidence of kidney damage (such as persistent albuminuria, imaging abnormalities, or structural disease).
If you get an abnormal result, do not panic. Repeat testing, trend analysis, and full clinical assessment are essential.
Limitations of Any CKD Calculator
- Creatinine can be affected by muscle mass, diet, hydration status, and medications.
- Acute illness can temporarily change kidney markers.
- Equation-based eGFR is less reliable in unusual body composition extremes.
- Pregnancy and pediatric cases need different approaches.
Practical Next Steps If Your Number Is Concerning
1) Confirm and repeat
Discuss repeat creatinine and urine ACR testing with your clinician after an appropriate interval.
2) Review blood pressure and diabetes status
Hypertension and diabetes are major CKD drivers. Good control can significantly slow progression.
3) Review medications and kidney safety
Some medicines require dose adjustment as kidney function changes. NSAID overuse can also be harmful in many CKD patients.
4) Build a kidney-protective routine
- Control blood pressure
- Manage blood sugar if diabetic
- Reduce sodium intake
- Avoid tobacco
- Maintain healthy weight and regular activity
- Keep follow-up appointments and lab checks
Frequently Asked Questions
Is one low eGFR enough to diagnose CKD?
No. CKD usually requires persistence over at least 3 months or other clear evidence of kidney damage.
Can eGFR improve?
Yes, especially if a temporary factor (dehydration, medication effect, acute illness) caused the abnormal value. Long-term trends are more informative than single measurements.
Should I use cystatin C too?
In selected patients, cystatin C can improve estimation accuracy, especially when creatinine-based estimates may be misleading.
Bottom Line
A CKD calculator is a useful screening and monitoring aid. It helps organize kidney risk into understandable categories, but it is not a replacement for medical care. Use this tool to start better conversations with your healthcare team and to track your kidney health over time.