A1C to Average Glucose Converter
Convert A1C to estimated average glucose (eAG) in mg/dL or mmol/L and back, with the ADA reference chart. Runs entirely in your browser.
Also available as a desktop app for Windows.
About this tool
A1C and average glucose measure the same thing from two sides. A1C is the percentage of hemoglobin that has glucose attached — a reading taken in a lab, on a blood draw. Estimated average glucose (eAG) is what that same number would look like on a glucose meter, averaged over the roughly 2–3 months that red blood cells live. This tool converts between the two in both directions, using the formula from the ADAG study that the American Diabetes Association adopted: eAG (mg/dL) = 28.7 × A1C − 46.7.
The conversion is linear, but the numbers do not feel linear: moving from A1C 6% to 7% adds 29 mg/dL, while moving from 9% to 10% adds another 29 on top of a much higher base. That is why the chart below lists 19 rows instead of one formula — the step from 5% to 6% and the step from 9% to 10% look small on paper and are not small in daily readings.
The three colored ranges come straight from the ADA’s diagnostic reference values: below 5.7% is below the prediabetes threshold, 5.7–6.4% is the prediabetes range, and 6.5% or above is the diabetes range. They are included so the number has context — they are a restatement of published thresholds, not this tool making a judgment about you.
Frequently asked questions
- Which formula does this use, and why that one?
- The ADAG study formula (Nathan et al., 2008): eAG (mg/dL) = 28.7 × A1C − 46.7, with mmol/L derived by dividing by 18.018. It was established across 10 laboratories and 3 A1C assay methods with continuous glucose monitoring as ground truth, which is why the American Diabetes Association adopted it as the standard conversion. Older "rule of 28" shortcuts predate it and drift by several mg/dL.
- My meter shows 110 mg/dL. Is that my A1C?
- Not directly — a single meter reading is one moment, while A1C is a 2–3 month average. Only an averaged glucose (for example from a continuous glucose monitor report, or a lab-calculated eAG) should be converted to A1C. Converting a single fasting reading of 110 mg/dL gives an "A1C" near 5.5%, but your actual A1C also depends on what happens after meals and overnight.
- Does the colored range mean I have diabetes?
- No. The tool restates the ADA’s published reference thresholds so the number has context. A diagnosis is made by a clinician using confirmed lab measurements, sometimes repeated, together with the rest of your history. Use this page to understand what a lab report says, not to diagnose anything.
- Does it send my numbers anywhere?
- No. The conversion is one line of arithmetic in the page. There is no server, no request and no logging, and the tool keeps working with the network switched off — a practical way to verify the claim yourself.