CKD Calculator (eGFR + Stage)
Estimate kidney function using the CKD-EPI 2021 creatinine equation (adults). Add urine ACR for a more complete CKD risk view.
Educational tool only. This does not diagnose CKD by itself. CKD usually requires persistent findings for at least 3 months and clinical interpretation by a licensed professional.
What this CKD calculator does
This calculator estimates your eGFR (estimated glomerular filtration rate), which is a common way to assess kidney function. The lower the eGFR, the more reduced kidney filtration may be. It also assigns a G-stage (G1 through G5), and if you provide urine ACR, it adds an A-category (A1 through A3) and a simple KDIGO-style risk level.
In short: eGFR helps answer, “How well are the kidneys filtering right now?” while urine ACR helps answer, “Is there evidence of kidney damage?”
How the formula works
This page uses the CKD-EPI 2021 creatinine equation (race-free), a widely used adult formula:
- Depends on age, sex, and serum creatinine.
- Returns eGFR in mL/min/1.73m².
- Best interpreted in stable clinical settings (not during acute illness or rapidly changing kidney function).
If your lab reports creatinine in µmol/L, the calculator converts it to mg/dL before applying the equation.
How to interpret CKD G-stages
eGFR categories
- G1: 90 or higher (normal/high range, but CKD may still exist if other abnormalities are 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: below 15 (kidney failure range)
Important: a single result is only a snapshot. Clinical diagnosis usually requires repeat values and the broader context of blood pressure, urine findings, imaging, medications, and medical history.
Why urine ACR matters
Urine albumin-to-creatinine ratio (ACR) can reveal kidney damage before eGFR drops severely. ACR categories:
- A1: <30 mg/g (normal to mildly increased)
- A2: 30–300 mg/g (moderately increased)
- A3: >300 mg/g (severely increased)
Combining G-stage and A-category gives a much better estimate of long-term kidney and cardiovascular risk than either one alone.
What to do if your estimate is low
Practical next steps
- Repeat testing when your clinician recommends it, especially if this is your first abnormal result.
- Check urine ACR if not already done.
- Review blood pressure, blood sugar, and medication list (including NSAID use).
- Discuss kidney-protective strategies, especially if you have diabetes, hypertension, or heart disease.
Kidney-protective habits that matter
- Keep blood pressure in target range.
- Optimize glucose control if you have diabetes.
- Avoid dehydration and unnecessary nephrotoxic drugs.
- Moderate sodium intake and prioritize whole-food nutrition.
- Exercise regularly, avoid tobacco, and maintain a healthy weight.
- Stay current with routine labs and follow-up appointments.
Limitations of online CKD calculators
No online calculator can replace a medical evaluation. eGFR estimates may be less accurate in pregnancy, very unusual muscle mass states, acute kidney injury, hospitalization, and certain chronic illnesses. In some cases, clinicians may order cystatin C-based equations, timed urine studies, or additional diagnostics for better precision.
Bottom line
A CKD calculator is a useful screening and education tool. Use it to understand your numbers, track trends, and have a better conversation with your clinician. For decisions about diagnosis or treatment, always rely on professional medical guidance.