What formula does the GFR Calculator use?

It uses the CKD-EPI 2021 creatinine equation, a race-free formula that estimates GFR from serum creatinine, age, and sex. It is the current standard many laboratories use to report eGFR.

What do the CKD stages G1 to G5 mean?

They classify kidney function by eGFR: G1 is 90 or above (normal), G2 is 60–89 (mildly reduced), G3a is 45–59, G3b is 30–44, G4 is 15–29 (severely reduced), and G5 is under 15 (kidney failure).

Is the GFR Calculator's result the same as my lab's eGFR?

It should be close if the same equation and inputs are used, but labs may apply slightly different rounding or use an older equation, so treat this as an estimate to discuss with your clinician, not a replacement for a lab report.

Does the GFR Calculator need my race to compute eGFR?

No. It uses the CKD-EPI 2021 race-free equation, which removed the race coefficient used in earlier eGFR formulas and only needs creatinine, age, and sex.

Is the GFR Calculator's eGFR a diagnosis?

No. It gives a general estimate based on a standard formula. It is not a diagnosis and does not replace guidance from a doctor or other qualified healthcare professional.

Is my creatinine value uploaded when I use the GFR Calculator?

No. The GFR Calculator runs entirely in your browser. The numbers you type are used only to compute the result on your device and are never sent to ArrayKit or anywhere else.

GFR Calculator Online

Estimate your glomerular filtration rate (eGFR) and CKD stage from creatinine, age, and sex, right in your browser. A general estimate, not medical advice.

The GFR Calculator runs entirely in your browser. The creatinine, age, and sex you enter never leave your device and nothing is uploaded to ArrayKit. Results are a general estimate using a standard formula, not medical advice.

Open the Body Surface Area Calculator

About GFR Calculator

GFR Calculator estimates your glomerular filtration rate (eGFR) from a serum creatinine reading, your age, and your sex, using the CKD-EPI 2021 race-free equation that labs use to report kidney function. It shows the estimated eGFR in mL/min/1.73m² and classifies the result into a chronic kidney disease (CKD) stage from G1 (normal) through G5 (kidney failure), with a short description of what each stage means. It is handy for tracking a lab result over time, understanding a creatinine reading before a doctor visit, or seeing how eGFR shifts with age. Everything computes instantly on your device — your creatinine value is never uploaded. This is a general estimate using a standard formula, not medical advice — always confirm kidney function with a clinician and a laboratory-reported eGFR.

Features

Estimates eGFR from serum creatinine, age, and sex
Uses the CKD-EPI 2021 race-free equation, the current lab-reporting standard
Classifies the result into CKD stage G1 through G5
Shows the eGFR range and plain-language meaning for the matched stage
Copy a plain-text summary of the creatinine, eGFR, and stage
Instant results as you type, with no page reloads
Clear error message for missing or invalid creatinine or age
Runs entirely in your browser — your figures never leave your device

How to use the GFR Calculator

Enter your serum creatinine in mg/dL
Enter your age and select your sex
Read your estimated eGFR and CKD stage
Copy the summary or adjust the numbers to see how eGFR changes

Example

Input

Cr 1.0, male, 40y

Output

eGFR: ~97 (G1)

CKD-EPI 2021 estimates an eGFR of about 97 mL/min/1.73m², in the normal G1 range.

Common errors & troubleshooting

GFR Calculator shows an error even though numbers were entered. — Make sure both the creatinine value and the age are greater than zero, and that age is a realistic number (1–130).
eGFR seems too low compared to a lab report. — Confirm the creatinine value is in mg/dL, not µmol/L — labs outside the US often report µmol/L, which needs dividing by 88.4 first.
Result changes noticeably when switching sex. — The CKD-EPI 2021 equation uses different constants for male and female, so double-check the selected sex matches the person the reading is for.
eGFR looks normal but a doctor mentioned kidney concerns. — eGFR is only one marker — kidney damage markers like albuminuria matter too, so this estimate does not replace a full clinical assessment.

Frequently asked questions

What formula does the GFR Calculator use?: It uses the CKD-EPI 2021 creatinine equation, a race-free formula that estimates GFR from serum creatinine, age, and sex. It is the current standard many laboratories use to report eGFR.
What do the CKD stages G1 to G5 mean?: They classify kidney function by eGFR: G1 is 90 or above (normal), G2 is 60–89 (mildly reduced), G3a is 45–59, G3b is 30–44, G4 is 15–29 (severely reduced), and G5 is under 15 (kidney failure).
Is the GFR Calculator's result the same as my lab's eGFR?: It should be close if the same equation and inputs are used, but labs may apply slightly different rounding or use an older equation, so treat this as an estimate to discuss with your clinician, not a replacement for a lab report.
Does the GFR Calculator need my race to compute eGFR?: No. It uses the CKD-EPI 2021 race-free equation, which removed the race coefficient used in earlier eGFR formulas and only needs creatinine, age, and sex.
Is the GFR Calculator's eGFR a diagnosis?: No. It gives a general estimate based on a standard formula. It is not a diagnosis and does not replace guidance from a doctor or other qualified healthcare professional.
Is my creatinine value uploaded when I use the GFR Calculator?: No. The GFR Calculator runs entirely in your browser. The numbers you type are used only to compute the result on your device and are never sent to ArrayKit or anywhere else.

Related tools

Body Surface Area Calculator — Estimate body surface area (BSA) with Mosteller, Du Bois and other formulas.
BMI Calculator — Calculate body mass index and see the healthy weight range for your height.
BAC Calculator — Estimate blood alcohol content from drinks, weight, sex and time.
Ideal Weight Calculator — Estimate ideal body weight with the Devine, Robinson, Miller and Hamwi formulas.
BMR Calculator — Estimate your basal metabolic rate — the calories your body burns at rest.
Healthy Weight Calculator — Find the healthy weight range for your height from the normal BMI band.