GFR Calculator
Estimate your Glomerular Filtration Rate to assess kidney function using the race-free CKD-EPI 2021 equations, with an optional cystatin C input for the more accurate combined estimate.
Enter Your Values
Typical range: 0.5-1.3 mg/dL (44-115 µmol/L). Unit-specific limits are checked after you choose a unit.
mg/L, typical range 0.5-1.1. Adding it switches the calculator to the more accurate CKD-EPI 2021 combined equation.
Enter your values and press Calculate: you will get the result, its method, the inputs used and confidence, plus copy, print and share options.
How this calculator works
CKD-EPI 2021 (creatinine, race-free)v1.0.0
Current standard eGFR equation using creatinine, age and sex without a race coefficient.
- Applies to
- Adults; not valid in acute kidney injury, extremes of muscle mass, or pregnancy
- Assumptions
- Standardized creatinine assay
- Limitations
- An estimate, not a measured GFR; Single readings vary with hydration
- Output
- mL/min/1.73 m²
- Last reviewed
- 2026-06-01
Evidence Sources & Literature
- New England Journal of Medicine / NIDDK. New creatinine- and cystatin C-based equations to estimate GFR without race. N Engl J Med, 2021. doi:10.1056/NEJMoa2102953. <a href="https://www.niddk.nih.gov/health-information/professionals/clinical-tools-patient-management/kidney-disease/laboratory-evaluation/chronic-kidney-disease-guide" rel="nofollow noopener" target="_blank">Source</a>.
About the GFR Calculator
GFR (glomerular filtration rate) is a measure of how well your kidneys are filtering waste from your blood, and it is the main number doctors use to assess kidney function. This calculator estimates your GFR (technically eGFR, the e standing for estimated) from a blood test result called serum creatinine, along with your age and sex. It is an important clinical number, so I will explain it carefully.
I want to be very clear from the start: kidney health is a medical matter, and this calculator is for understanding your results, not for diagnosing yourself. If you have a creatinine result and want to make sense of it, this can help, but any decisions belong with your doctor.
What GFR tells you
Your kidneys filter your blood constantly, removing waste and excess fluid. GFR estimates the rate of that filtering, so it reflects how well your kidneys are working overall. A higher GFR generally means better filtering. Doctors use it to detect kidney disease early, to stage it if present, and to guide decisions like how to dose certain medications that the kidneys clear.
How it is estimated
True GFR is hard to measure directly, so it is estimated with validated equations that use your serum creatinine, age and sex. This calculator uses the CKD-EPI 2021 race-free creatinine equation by default, and if your lab report also includes serum cystatin C, entering it switches the calculation to the combined creatinine + cystatin C equation, which is the most accurate variant and less influenced by muscle mass. Creatinine is a waste product your muscles produce and your kidneys remove, so its level in the blood reflects kidney function. The calculator applies a standard equation to produce your eGFR in the usual units (mL/min/1.73 square meters).
How results are interpreted
As a broad guide, an eGFR of 90 or above is generally considered normal, with lower values prompting closer attention, and an eGFR under 60 sustained over three months is one marker of chronic kidney disease. But context is everything: eGFR naturally declines somewhat with age, a single reading can be affected by hydration and other factors, and trends over time matter more than one number. Your doctor interprets it alongside other tests like urine albumin.
An important boundary
Please treat this as an educational tool only. A single eGFR estimate does not diagnose kidney disease, and a low or unexpected result should always be discussed with your doctor, who can repeat the test, look at trends, and consider the full picture. Do not change medications, fluids or diet based on a calculator. Use this to understand the concept and your numbers, and let your medical team guide any action.
Dietitian Insight: Estimated glomerular filtration rate (CKD-EPI 2021) evaluates kidney filtration function without race coefficients. Learn about metabolic filtering and systemic health, or calculate baseline volume demands with our renal fluid intake calculator.
Sources & method
This calculator uses established, peer-reviewed formulas and reference ranges from recognized health and nutrition authorities. Results are estimates for general education, not a medical diagnosis. For decisions about your health, consult a qualified clinician. Reviewed by Macro & Meals Editorial Team, Content editor.
Frequently Asked Questions
What is a normal GFR?
As a broad guide, an eGFR of 90 or above is generally considered normal, and an eGFR under 60 sustained for three months is one marker of chronic kidney disease. However, eGFR declines somewhat with age and a single reading can be affected by other factors, so your doctor interprets it in context.
How is GFR estimated?
True GFR is hard to measure directly, so it is estimated with validated equations such as CKD-EPI that use your serum creatinine, age and sex. Creatinine is a waste product your kidneys remove, so its blood level reflects kidney function. The result is reported in mL/min/1.73 square meters.
Can I diagnose kidney disease with this calculator?
No. A single eGFR estimate does not diagnose kidney disease. A low or unexpected result should be discussed with your doctor, who can repeat the test, look at trends over time, and consider other tests like urine albumin. This tool is for understanding your numbers, not for self-diagnosis.
What can affect my GFR result?
eGFR naturally declines somewhat with age, and a single reading can be influenced by hydration, muscle mass and other factors, since it is based on creatinine. That is why trends over time matter more than one value, and why your doctor interprets it alongside the full clinical picture.
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