GFR Calculator

Estimated glomerular filtration rate — the standard measure of kidney function. Uses the CKD-EPI 2021 (race-free) equation.

Estimated GFR

mL / min / 1.73 m²

—

CKD stage

—

Description

—

⚕ This is a screening estimate. Diagnosis of chronic kidney disease requires repeat testing over 3+ months and clinical context. Talk to your doctor.

What GFR measures

The glomerular filtration rate is how much fluid your kidneys filter per minute. Healthy adults filter ~120 mL/min — the equivalent of ~180 L of plasma per day. (You don't urinate that much because the tubules reabsorb most of it.)

Creatinine is a muscle breakdown product cleared by the kidneys. If kidney function drops, creatinine rises. The CKD-EPI equation back-calculates GFR from creatinine, adjusting for age and sex.

The 2021 race-free update

Until 2021, GFR equations included a race coefficient that gave Black patients ~1.16× higher estimates for the same creatinine — based on body composition assumptions that have since been challenged as harmful. The new CKD-EPI 2021 formula removed the race term. This calculator uses the new version.

CKD stages

  • G1 (≥90): Normal kidney function — but with markers of damage (proteinuria) you'd still have CKD.
  • G2 (60–89): Mild decrease, very common.
  • G3a (45–59), G3b (30–44): Moderate decrease — many people don't have symptoms here.
  • G4 (15–29): Severe. Specialist care.
  • G5 (<15): Kidney failure. Dialysis or transplant territory.