Estimate kidney function (eGFR) from serum creatinine with CKD-EPI 2021.
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How is eGFR (kidney function) calculated?
The 2021 CKD-EPI creatinine equation estimates eGFR from serum creatinine, age and sex (no race coefficient), normalised to a body surface area of 1.73 m². It measures how much blood the kidneys filter each minute. For example, a 50-year-old man with a creatinine of 1.0 mg/dL has an eGFR of about 92 mL/min/1.73m² — stage G1. A single result is not a diagnosis.
Understanding your result
eGFR estimates how much blood the kidneys filter each minute. Higher is generally better; values below 60 for three months or more suggest chronic kidney disease. A single result is not a diagnosis.
Formula and method
The 2021 CKD-EPI creatinine equation uses serum creatinine, age and sex (no race coefficient) to estimate eGFR, normalised to a body surface area of 1.73 m².
Assumptions and limitations
The eGFR here is an estimate from a single creatinine value using the 2021 CKD-EPI equation; it is informational and not a diagnosis. Creatinine can shift with muscle mass, diet, hydration and illness, and one result cannot confirm kidney disease. Only a clinician can interpret it alongside your history and other tests.
Worked example
A 50-year-old man with a creatinine of 1.0 mg/dL has an eGFR of about 92 mL/min/1.73m² — stage G1.
How to use this tool
- Enter your serum creatinine in mg/dL.
- Enter your age and sex.
- Read your eGFR and CKD stage.
Common mistakes to avoid
- Entering creatinine in µmol/L instead of mg/dL (divide µmol/L by 88.4).
- Treating one reading as a diagnosis — staging needs repeat tests.
About the GFR Calculator
The GFR Calculator estimates your glomerular filtration rate (eGFR) — a measure of kidney function — from your serum creatinine, age and sex, using the race-free 2021 CKD-EPI equation, and shows the CKD stage.
Who should use this tool
Healthcare students and professionals, and patients tracking kidney results.
Benefits
- Modern, race-free CKD-EPI 2021 equation.
- eGFR in mL/min/1.73m².
- Maps the result to a CKD stage.
- Instant and private.
Practical use cases
- Interpreting a creatinine blood result.
- Tracking kidney function over time.
- Learning the CKD staging.
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Frequently asked questions
What is a normal eGFR?
Around 90 or above is considered normal, though it naturally declines with age. Below 60 for three months or more may indicate chronic kidney disease.
Is this a diagnosis?
No. It is an estimate for information only. Diagnosis and staging require a clinician and repeat testing.
Why does the result assume a standard body size?
The equation reports eGFR normalised to a body surface area of 1.73 square metres, a common reference value, so results can be compared consistently between people. For someone with a very different body size the standardised figure may need clinical adjustment, which your care team can advise on.