GFR Calculator
Estimate glomerular filtration rate (eGFR) using the race-free 2021 CKD-EPI creatinine equation.
Normal
An eGFR of 92 mL/min/1.73m² places you in the "Normal (Stage 1)" range.
- CKD StageNormal (Stage 1)
Uses the 2021 CKD-EPI race-free creatinine equation. This is a screening estimate, not a diagnosis — discuss results with a clinician.
About the GFR Calculator
Glomerular filtration rate (GFR) estimates how well your kidneys are filtering blood, and this calculator reproduces the 2021 CKD-EPI creatinine equation — the current standard, race-free formula used in most U.S. labs — from your age, sex, and a serum creatinine value you'd typically get from a routine blood test.
This is an estimate built from a lab number you already have, not a new diagnostic test. eGFR from a single creatinine reading can be thrown off by dehydration, recent muscle-heavy exercise, muscle mass itself, and other factors your doctor accounts for when interpreting results — a single number here isn't a diagnosis of kidney disease.
People typically use this after getting bloodwork back to understand what the creatinine number on a lab report actually translates to in eGFR terms and CKD stage, or to track how a result compares to a previous one.
You need a specific creatinine value from a real blood draw to use this meaningfully, but the number itself is calculated locally — nothing about your labs is transmitted or saved anywhere outside your own device.
How it’s calculated
The 2021 CKD-EPI equation uses your creatinine relative to a sex-specific reference value (kappa), raised to a power that differs depending on whether your creatinine is above or below that reference — then adjusted by an age-based decay factor, since kidney function typically declines gradually with age.
The 2021 version removed the race coefficient used in earlier CKD-EPI formulas, following recommendations that race-based adjustments weren't clinically justified — this calculator uses only age, sex, and creatinine, matching current U.S. lab standard practice.
Frequently asked questions
What is a normal eGFR result?
An eGFR of 90 or above is generally considered normal kidney function (Stage 1 if other kidney damage markers are present, or simply normal otherwise) — values below that are grouped into progressively lower CKD stages, though a single reading isn't diagnostic on its own.
Why does this calculator ask for sex but not race?
It implements the 2021 CKD-EPI creatinine equation, which removed the race coefficient present in the older 2009 version after evaluation found race-based adjustment wasn't clinically well justified — sex is still a factor because average muscle mass and creatinine production differ by sex.
Can a single creatinine test accurately diagnose kidney disease?
Not on its own — creatinine and eGFR can fluctuate with hydration, recent exercise, and diet, so clinicians typically look at trends across multiple tests and often confirm findings with additional markers before diagnosing CKD.
What can cause a falsely low or high eGFR reading?
Dehydration, high muscle mass, recent intense exercise, and certain medications can all shift creatinine levels temporarily without reflecting an actual change in kidney function, which is one reason a single reading is interpreted cautiously.
What should I do if my eGFR result is low?
Discuss it with a healthcare provider — this calculator can tell you what stage a creatinine value falls into by the standard formula, but it can't evaluate your overall clinical picture or recommend next steps the way a doctor can.
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