GFR Calculator
Calculate your estimated glomerular filtration rate (eGFR) and CKD stage using the 2021 race-free CKD-EPI creatinine equation.
Example
A 50-year-old male with a serum creatinine of 0.9 mg/dL:
kappa = 0.9, alpha = -0.302 (male)
ratio = 0.9 / 0.9 = 1.0
eGFR = 142 x min(1,1)^-0.302 x max(1,1)^-1.200
x 0.9938^50 x 1
= 142 x 1 x 1 x 0.7339
= 104 mL/min/1.73m2 -> CKD stage G1 (Normal or high)How it works
Enter serum creatinine (mg/dL), age, and sex; the tool applies the CKD-EPI 2021 piecewise formula and reports eGFR in mL/min/1.73m2 with the matching CKD stage.
Good to know
This GFR Calculator estimates your glomerular filtration rate (eGFR) from three inputs you can read off a basic blood panel: serum creatinine, age, and sex. It uses the 2021 race-free CKD-EPI creatinine equation and instantly maps the result to a chronic kidney disease (CKD) stage from G1 to G5. It's aimed at anyone who has a recent metabolic panel and wants to understand what their creatinine number translates to in terms of kidney filtering capacity.
Reach for it when a lab report lists creatinine but no eGFR, when your lab caps high values at "≥60" and you want a concrete figure, or when you want to recompute using the newer race-free formula instead of an older result that may have included a race coefficient. It's also handy for tracking a trend over several tests, since a single reading is heavily affected by hydration, recent meat intake, and muscle mass.
To read the result: the eGFR is reported in mL/min/1.73m², where higher is better. Roughly 90 and above is normal (G1), 60 to 89 is mildly reduced (G2), and anything below 60 that persists across repeat tests points toward CKD stages G3 through G5. The calculator shows the matching stage and a plain-language label so you can place a number in context, but a stage is not a diagnosis on its own.
A few practical caveats:
- Creatinine-based eGFR is less accurate at the extremes of muscle mass (bodybuilders, amputees, frail or very elderly people) and right after a high-protein meal or creatine supplement, so consider timing and a repeat test before drawing conclusions.
Frequently asked questions
Why does this calculator not ask for race?
It uses the 2021 CKD-EPI creatinine equation, which the NKF-ASN task force recommended specifically to remove the race coefficient. The updated formula estimates GFR using only creatinine, age, and sex.
What CKD stage matches my eGFR?
G1 is 90+, G2 is 60-89, G3a is 45-59, G3b is 30-44, G4 is 15-29, and G5 is below 15 mL/min/1.73m2. Stages G3-G5 generally warrant follow-up with a clinician, ideally with repeat testing.
Is my data uploaded anywhere?
No — this calculator runs entirely in your browser; nothing is uploaded.
Is this a substitute for medical advice?
No. These are educational estimates — consult a qualified health professional for medical decisions.
People also ask
What is a normal GFR by age?
GFR naturally declines with age, so a healthy 30-year-old often has an eGFR around 100 or higher, while values in the 70s to 80s can be typical for someone in their 60s or 70s. The CKD-EPI 2021 equation already factors age into the calculation, which is why an identical creatinine value yields a lower eGFR for an older person.
Can I calculate eGFR if my creatinine is in micromoles per liter (umol/L) instead of mg/dL?
This tool expects creatinine in mg/dL. To convert from umol/L, divide the value by 88.4 (for example, 80 umol/L is about 0.9 mg/dL) before entering it.
What does it mean if my eGFR is below 60?
An eGFR under 60 indicates reduced kidney filtering capacity, and if it persists for three months or more it meets one criterion for chronic kidney disease. A single low reading is not conclusive because creatinine fluctuates, so repeat testing is typically used to confirm a trend.
Why did my eGFR change between two blood tests?
eGFR can shift between tests due to hydration status, recent high-protein meals, intense exercise, creatine supplements, certain medications, and normal lab measurement variation. Because of this, clinicians usually look at the trend across multiple readings rather than reacting to one value.
What is the difference between eGFR and creatinine clearance?
eGFR is a standardized estimate of filtration rate calculated from blood creatinine, age, and sex, while creatinine clearance is measured from a timed urine collection alongside a blood sample. Creatinine clearance tends to overestimate true GFR slightly because the kidneys secrete a small amount of creatinine in addition to filtering it.
Does the CKD-EPI 2021 equation work for people under 18?
No. The CKD-EPI 2021 creatinine equation is validated for adults aged 18 and older, and this calculator enforces that minimum. Pediatric eGFR is estimated with different formulas designed for children.
Can high creatinine readings be caused by something other than kidney disease?
Yes. Temporary or non-kidney factors such as dehydration, a high-meat meal, vigorous exercise, large muscle mass, and creatine supplements can raise serum creatinine and lower the calculated eGFR. This is why an unexpected result is often rechecked under more controlled conditions.
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