GFR Calculator
Enter serum creatinine in mg/dL or μmol/L, your age (18 to 120) and your sex. The calculator estimates your glomerular filtration rate (GFR), a measure of kidney function, with the race-free CKD-EPI 2021 equation. It shows the result in mL/min/1.73 m² to one decimal, along with the matching GFR category from G1 to G5. An empty field, an age outside that range or a creatinine outside 0.1 to 75 mg/dL (9 to 6,630 μmol/L) gets a message. A figure above 25 mg/dL or below 25 μmol/L looks like a reading in the other unit, so the calculator asks you to check the unit on your lab report before it shows a result.
CKD-EPI 2021 equation (race-free). Read the result with your doctor. It does not replace a lab test or a diagnosis.
How to use the GFR Calculator
- Enter your numbers in the GFR Calculator above.
- Press the Calculate eGFR button to see the result.
- To try other numbers, change any value and press the button again.
The CKD-EPI 2021 equation
eGFR = 142 × min(SCr/κ, 1)^α × max(SCr/κ, 1)^−1.200 × 0.9938^Age × 1.012 (if female)
SCr is serum creatinine in mg/dL. κ is 0.7 for women and 0.9 for men, and α is −0.241 for women and −0.302 for men. A value in μmol/L is divided by 88.4 to turn it into mg/dL. The result is mL/min/1.73 m². The 2021 version removed the historical race coefficient. The category comes from the eGFR as printed, so a result that prints as 90 is G1.
Worked example
A 50-year-old woman with serum creatinine 0.9 mg/dL gets an eGFR of 77.9 mL/min/1.73 m², category G2. At 70 with the same creatinine the result is 68.8, still G2. A 50-year-old man at 0.9 mg/dL gets 104, category G1.
Frequently asked questions
What is a normal GFR?
The National Kidney Foundation says an eGFR of 90 or higher is in the normal range, 60 to 89 may mean early-stage kidney disease, 15 to 59 may mean kidney disease, and below 15 may mean kidney failure. The equation also lowers the estimate with age. Each extra year multiplies it by 0.9938, which takes off about 0.6%. Ask your doctor what your own result means.
Does G1 or G2 mean I have kidney disease?
Not on its own. The National Kidney Foundation says that without evidence of kidney damage, neither G1 nor G2 meets the criteria for chronic kidney disease. Protein in the urine is one such sign, and this calculator does not ask about it. That makes the label a GFR category, not a diagnosis.
Does one low result mean I have chronic kidney disease?
No. The National Kidney Foundation says chronic kidney disease means your kidneys have been damaged or not working well for at least 3 months, and that an eGFR under 60 for 3 months or more may be a sign of it. One result cannot show 3 months, so a single 50 is category G3a and not a diagnosis. Ask your doctor whether to repeat the test.
What causes low GFR?
The calculator cannot tell you, because it only knows your creatinine, age and sex. The National Kidney Foundation names diabetes, high blood pressure, overweight or obesity, age over 60 and family history as risk factors for chronic kidney disease. It also says some medicines can affect your kidneys or change your test results.
Does this replace lab tests?
No. The calculator needs a serum creatinine value from a recent lab test, and it helps you read that result. It does not replace a lab test or a doctor's advice.