The GFR Calculator estimates estimated glomerular filtration rate (eGFR) from serum creatinine, age and sex using the 2021 race-free CKD-EPI creatinine equation as the default. Enter creatinine in mg/dL or µmol/L, read the eGFR in mL/min/1.73 m², and view the KDIGO stage bands as a reference table only. Staging and any decision about kidney health belong with a qualified clinician.
This page computes a number for education. It does not diagnose chronic kidney disease, does not recommend treatment, and does not replace laboratory reports or clinical judgement. A single eGFR can fluctuate with hydration, illness and medication; interpretation needs the rest of the clinical picture.
Estimate your glomerular filtration rate
Glomerular filtration rate describes how much blood the kidneys filter per unit time. Direct measurement is complex, so clinics use estimated GFR (eGFR) from creatinine and demographic inputs. The GFR Calculator returns that estimate and shows which KDIGO eGFR band the number falls near, labelled explicitly as reference, not a diagnosis.
Required inputs are serum creatinine, age and sex. Creatinine may be entered in mg/dL or µmol/L; the tool converts using µmol/L = mg/dL × 88.42 from the health reference. The primary output is eGFR in mL/min/1.73 m², rounded for display.
The figure is an estimate for general information. It is not medical advice. Only a clinician can say what a given eGFR means for a specific person, alongside urine tests, imaging, trends and history.
Apply the 2021 CKD-EPI equation
The default formula is the 2021 CKD-EPI creatinine equation, which removed the race coefficient used in earlier versions. In outline form:
eGFR = 142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^(−1.200) × 0.9938^age × (1.012 if female)κ is 0.7 for female and 0.9 for male. α is −0.241 for female and −0.302 for male. Scr is serum creatinine in mg/dL. The result is standardised to body surface area units of mL/min/1.73 m².
An MDRD-style alternative without a race coefficient is available in the engine for comparison, but CKD-EPI 2021 is the page default and the equation this copy centres. Laboratory reports increasingly cite 2021 CKD-EPI; matching that default avoids mixing eras of equations on one screen.
Do not adjust the result by hand for race. The 2021 update removed that coefficient because it was a biologically unfounded adjustment; this tool uses only the race-free form.
Enter creatinine in mg/dL or µmol/L
Creatinine units differ by region and by lab printout. Milligrams per decilitre (mg/dL) are common in the United States; micromoles per litre (µmol/L) are common elsewhere. The conversion in the reference file is:
µmol/L = mg/dL × 88.42So 1.0 mg/dL corresponds to 88.42 µmol/L. Enter the value in the unit shown on the lab report and set the unit control to match. Mixing a µmol/L number with an mg/dL setting produces a meaningless eGFR.
Creatinine alone is not kidney function. Muscle mass, diet, some drugs and assay methods move creatinine without a matching change in true GFR. That is one reason eGFR is an estimate and why clinicians read it in context.
Read the CKD stage reference
KDIGO groups eGFR into stages G1 through G5 for reference. The GFR Calculator shows this table as educational context. Matching a number to a row is not the same as receiving a CKD diagnosis, which also considers albuminuria and clinical assessment.
| Stage | eGFR (mL/min/1.73 m²) | Description (reference) |
|---|---|---|
| G1 | ≥90 | Normal or high |
| G2 | 60 to 89 | Mildly decreased |
| G3a | 45 to 59 | Mild to moderate |
| G3b | 30 to 44 | Moderate to severe |
| G4 | 15 to 29 | Severely decreased |
| G5 | <15 | Kidney failure |
On the result, the nearby band is described as a reference band and marked as not a diagnosis. The page never tells the reader what to do about a stage label. Decisions about further testing, referral or treatment sit with a clinician.
A value near a boundary can flip bands from day to day when creatinine moves slightly. Trends and confirmatory tests matter more than one screenshot of a calculator.
Understand why interpretation needs a doctor
eGFR is one marker among several. Albumin in urine, blood pressure, medications, acute illness, obstruction and prior kidney disease all change what a number means. Acute kidney injury and chronic disease are different problems that can share a low reading on a bad day.
Hydration status and recent meat-heavy meals can shift creatinine. Pregnancy, extremes of muscle mass and certain drugs need specialised interpretation the equation does not encode. Children and some uncommon assays sit outside the casual adult use case this educational tool assumes.
The honest use of this page is to understand how the 2021 equation turns creatinine, age and sex into an eGFR, and to see how laboratories label bands. The honest next step with any concerning or unexpected result is a conversation with a doctor who has the full record, not a self-assigned stage from a web form.
Understand the race-free update
Earlier eGFR equations applied a race coefficient that raised reported eGFR for patients labelled Black. That adjustment lacked a sound biological basis and could delay recognition of kidney disease. The 2021 CKD-EPI creatinine equation removed race from the inputs. This calculator implements that race-free equation as the default.
It does not offer a race toggle. The health reference states the same policy: earlier coefficients are not used here.
If an older lab report still cites a race-adjusted equation, the number may not match a 2021 recalculation on the same creatinine. Ask the reporting laboratory or clinician which equation was used rather than forcing the figures to agree by hand.
Worked example: creatinine 1.0 mg/dL, male, age 50
Take a male adult aged 50 with serum creatinine 1.0 mg/dL, CKD-EPI 2021. 1. Set constants for male sex. κ = 0.9, α = −0.302, female factor = 1 **2.
Evaluate the 2021 equation. Scr/κ = 1.0 / 0.9 ≈ 1.111, so min(Scr/κ, 1) = 1 and max(Scr/κ, 1) ≈ 1.111 eGFR ≈ 142 × 1^(−0.302) × (1.111)^(−1.200) × 0.9938^50 ≈ 92** mL/min/1.73 m² when rounded
3. Place the number on the reference table only. About 92 sits near the G1 reference description (normal or high) on the KDIGO eGFR bands. That adjacency is educational labelling on this page. It is not a diagnosis of kidney health, and it is not clearance to ignore other markers.
In µmol/L terms, the same creatinine is 1.0 × 88.42 = 88.42 µmol/L. Entering that value with the µmol/L unit selected should reproduce the same eGFR after conversion.
What this does not tell you: whether the person has kidney disease, whether medication doses need change, or whether the result is stable. Those questions belong in clinic.
Frequently asked questions
What is eGFR?
eGFR is estimated glomerular filtration rate, a calculated index of kidney filtration derived from creatinine (and sometimes other markers) plus age and sex. It is reported in mL/min/1.73 m². It is an estimate, not a direct measurement of GFR.
Is this calculator a diagnosis of CKD?
No. Chronic kidney disease staging is a clinical process that uses eGFR, albuminuria and other findings over time. This tool shows reference eGFR bands for education and states plainly that staging and decisions belong with a clinician.
Why is the 2021 equation race-free?
Earlier equations included a race coefficient that has been removed because it was not biologically justified and could misclassify risk. The 2021 CKD-EPI creatinine equation does not use race, and neither does this page.
How do I convert creatinine units?
Multiply mg/dL by 88.42 to get µmol/L, or divide µmol/L by 88.42 to get mg/dL. Match the unit control to the lab report before reading eGFR.
What eGFR is "normal"?
On the KDIGO reference table, G1 is eGFR ≥90 described as normal or high, and G2 is 60 to 89 described as mildly decreased. Those labels are reference descriptors for education here. A clinician decides what a result means for an individual, including whether further tests are needed.
Can eGFR change from day to day?
Yes. Creatinine moves with hydration, illness, medication and lab variation, so eGFR moves with it. Trends and confirmatory testing matter more than one isolated value.
Should I change medication based on this result?
No. Drug dosing and medication changes that depend on kidney function are clinical decisions. This page computes eGFR for education only and does not recommend actions.
Does MDRD still matter?
MDRD without a race coefficient is offered in the engine as an alternative some older materials still cite. CKD-EPI 2021 is the default and the equation this page explains in full. Prefer the equation named on the laboratory report when comparing numbers.
Summary
The GFR Calculator estimates eGFR with the 2021 race-free CKD-EPI creatinine equation from creatinine, age and sex, with optional µmol/L entry via the 88.42 conversion factor. For creatinine 1.0 mg/dL in a male aged 50, eGFR rounds near 92 mL/min/1.73 m², adjacent to the G1 reference band on the KDIGO table.
Stage rows are reference only, not diagnoses. Interpretation, staging and any clinical decision belong with a qualified clinician; a single calculator result is educational and incomplete on its own.