GFR Calculator
Estimate eGFR and kidney function stage with the CKD-EPI 2021 formula from your creatinine, age and sex.
eGFR
86.2 mL/min/1.73m²
CKD-EPI 2021 formula (race-free)
Kidney function stage
Stage G2
Mildly reduced (60–89)
eGFR is one number used to assess kidney function. Results vary with hydration, muscle mass and lab method — only a doctor can interpret your result in context.
Last updated: February 2026
How this calculator is verified
Checked by True Calculator automated test suite on
- Formula verified against a published worked example in the automated test suite
- Edge cases (zero, negative, boundary and unit-mismatch inputs) covered by unit tests
The full verification method is on our how we verify page. Found an error? Tell us and we will re-check it.
When to Use This Calculator
Use the GFR calculator when you have a creatinine result from a blood test and want to understand what it means before your doctor's appointment. Annual health check-ups in India increasingly include creatinine, and patients often leave the lab with a number but no interpretation — this tool turns it into an eGFR and a standard G1–G5 stage that matches how nephrologists talk about kidney function. It is also useful for people with diabetes or hypertension, the two biggest risk factors for kidney disease, who want to track their function over time and catch a downward trend early. The CKD-EPI 2021 formula is the modern standard, so the estimate aligns with what most labs now report. Remember: it is a screening estimate for awareness, not a diagnosis.
How to Use This Calculator
- Step 1: Choose your sex.
- Step 2: Enter your age in years.
- Step 3: Enter your serum creatinine in mg/dL, from a recent blood test report.
- Step 4: Read your estimated eGFR and the corresponding kidney function stage.
Worked Example
A 60-year-old man with serum creatinine of 1.0 mg/dL gets an eGFR of 86.2 mL/min/1.73m² from the CKD-EPI 2021 equation, placing him in stage G2 (mildly reduced). A 45-year-old woman with 0.8 mg/dL reaches 92.5 — stage G1, normal function. A 40-year-old man with 2.1 mg/dL drops to 40.1, stage G3b. The formula combines creatinine, age and sex: creatinine lowers the result, while age does too, which is why the same value at 70 years scores lower than at 30 years.
Tips and Common Mistakes
- •Tip 1: Use a recent, fasting lab value — hydration and heavy meals can shift creatinine.
- •Tip 2: Repeat the test before drawing conclusions; single readings fluctuate with hydration and activity.
- •Tip 3: Bring the result to your doctor rather than interpreting it alone — context like urine tests and blood pressure matters.
- ✗Mistake 1: Panicking over a single low value — dehydration, creatine supplements and muscle mass all affect it.
- ✗Mistake 2: Using an old report; creatinine levels change over months, so always use the latest test.
Frequently Asked Questions
What is eGFR and why does it matter?
eGFR is an estimate of how many millilitres of blood your kidneys filter per minute per 1.73 m² of body surface. It is the main screening number used to assess kidney function and stage chronic kidney disease.
Which formula does this calculator use?
The CKD-EPI 2021 equation, which uses age, sex and serum creatinine without race adjustment. It has replaced older formulas like MDRD in most modern laboratories.
My eGFR came out low — should I worry?
Not automatically. eGFR falls naturally with age, and a single value can be affected by dehydration, recent meat intake, muscle mass and lab variation. One reading is never a diagnosis — your doctor will repeat it and look at the full picture.
What are the G1–G5 stages?
They are the international kidney-disease stages: G1 (≥90) and G2 (60–89) are normal to mildly reduced, G3a/G3b cover 30–59, G4 is 15–29 and G5 is below 15. Stage alone never tells the full clinical story.
What can I do to keep my kidneys healthy?
Control blood pressure and blood sugar, stay well hydrated, avoid routine painkillers (NSAIDs) without need, limit salt and get checked if you have diabetes or a family history of kidney disease.
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