GFR Calculator

Glomerular Filtration Rate (GFR) is the volume of blood your kidneys filter per minute, normalised to a body surface area of 1.73 m². It is the single best overall measure of kidney function. Because direct GFR measurement is invasive and expensive, clinicians use eGFR — an estimate calculated from a simple blood creatinine test. A low or falling eGFR is the earliest sign of chronic kidney disease, often years before symptoms appear.

The CKD-EPI 2021 equation is the latest version of the Chronic Kidney Disease Epidemiology Collaboration formula. In 2021, the National Kidney Foundation and American Society of Nephrology officially recommended removing the prior race coefficient. The new race-free formula uses only serum creatinine, age, and sex, and is now the recommended equation in the United States. Our calculator implements this exact formula.

A normal eGFR for a healthy young adult is around 100 mL/min/1.73 m². Values of ≥ 90 are considered normal (stage G1). It is also normal for eGFR to drop with age — roughly 1 mL/min per year after 40 — so a healthy 70-year-old commonly has an eGFR around 75–85 without having kidney disease. The KDIGO bands are: G1 ≥90, G2 60–89, G3a 45–59, G3b 30–44, G4 15–29, G5 < 15.

No. By definition, chronic kidney disease requires a persistently low eGFR (< 60) for at least 3 months, or other evidence of kidney damage such as albuminuria, abnormal imaging, or histology. A single abnormal eGFR can be caused by dehydration, recent heavy exercise, a high-protein meal, certain medications, or a lab artifact. Always retest before drawing conclusions.

Earlier CKD-EPI equations applied a multiplier for self-identified Black patients, which research now shows could overestimate eGFR and delay diagnosis in Black patients. In 2021 a joint NKF–ASN task force recommended removing race entirely. The CKD-EPI 2021 race-free equation is now standard across US laboratories and is the version this calculator uses.

They are the same measurement in different units. US labs report serum creatinine in milligrams per decilitre (mg/dL). The rest of the world uses the SI unit micromoles per litre (µmol/L). The conversion is: µmol/L = mg/dL × 88.4 (e.g., 1.0 mg/dL ≈ 88 µmol/L). Our calculator lets you enter either and converts automatically.

Yes. Creatinine is a waste product of muscle metabolism, so very muscular people naturally produce more of it and can have a higher serum creatinine without kidney damage — which translates to a lower estimated GFR. Conversely, people with very low muscle mass (the frail elderly, amputees) produce less creatinine and may have a falsely high eGFR. For these groups a cystatin C–based eGFR is often more accurate.

Early CKD (eGFR 45–89) is usually completely symptom-free, which is why screening blood tests matter. As eGFR drops below 30, symptoms can include fatigue, swelling in the ankles or face, foamy urine, itchy skin, poor appetite, nausea, and difficulty concentrating. At eGFR < 15 (stage G5), dialysis or transplant becomes necessary. If you have these symptoms and a low eGFR, see a nephrologist.

You generally can't reverse permanently lost kidney function, but you can slow further decline. The biggest levers are: tight blood pressure control (target < 130/80), tight blood sugar control if diabetic, stopping smoking, avoiding NSAIDs and other nephrotoxic drugs when possible, staying well-hydrated, and treating any underlying cause (diabetes, hypertension, glomerulonephritis). For diabetic CKD, modern SGLT2 inhibitors meaningfully slow progression.

National kidney guidelines (KDIGO) recommend a nephrology referral when eGFR is persistently below 30, when there is significant albuminuria (ACR ≥ 300 mg/g), when eGFR drops rapidly, or when there is uncertainty about the cause of CKD. For an eGFR in the 30–59 range your primary-care doctor can usually manage things, but they may still refer you for an opinion or for medication selection.

No. This eGFR calculator is an educational tool intended to help you understand your lab report. It does not replace evaluation by a qualified clinician. A nephrologist will also consider your urine albumin, blood pressure, medications, comorbidities, prior eGFR trend, and clinical context — none of which the calculator can see. Always discuss abnormal results with your doctor.

The mathematics is exact — our implementation follows the published CKD-EPI 2021 equation and matches the eGFR that a clinical laboratory would report. Real-world accuracy depends on the inputs: an accurate, recent, fasting morning creatinine measured on a properly calibrated, IDMS-traceable assay produces the most reliable estimate. Like every creatinine-based equation, it is less accurate at the extremes of muscle mass and during acute kidney injury.