About the A1C to eAG
Converts a hemoglobin A1C percentage into an estimated average glucose (eAG) reading, shown in both mg/dL and mmol/L, the same units used on standard blood glucose meters. It also flags where that A1C falls relative to the American Diabetes Association's diagnostic categories. This is useful for translating a lab-reported percentage into a number that reads more like an everyday glucose meter result.
How It Works
Enter your A1C percentage and the calculator plugs it into a linear regression formula derived from the ADAG study to produce eAG in mg/dL, then converts that same value to mmol/L using the standard glucose unit conversion factor. It compares the entered A1C against three fixed thresholds to label it Normal, Prediabetes range, or Diabetes range.
Formula & Methodology
To work this by hand, multiply your A1C percentage by 28.7, then subtract 46.7 to get eAG in mg/dL. For an A1C of 7.0, that is 28.7 x 7.0 = 200.9, minus 46.7 = 154.2 mg/dL. Divide that mg/dL figure by 18.0182 to get the mmol/L equivalent used in most countries outside the US.
Examples
A1C of 6.5%
An A1C of 6.5% converts to eAG = 28.7 x 6.5 - 46.7 = 139.85, rounded to 140 mg/dL (7.8 mmol/L), and lands in the Diabetes range category since the threshold treats 6.5 as the start of that range.
A1C of 5.5%
An A1C of 5.5% works out to 28.7 x 5.5 - 46.7 = 111.15, rounded to 111 mg/dL (6.2 mmol/L), which falls under the Normal category since it sits below the 5.7% cutoff.
Advantages
- Translates a lab report percentage into the mg/dL or mmol/L units most people see on a home glucose meter.
- Shows both US and international units side by side without a separate conversion step.
- Flags the general diagnostic category alongside the number for quick context.
Common Mistakes
- Treating a single eAG estimate as equivalent to a real-time glucose reading, when it actually reflects an average over roughly the past 2-3 months.
- Assuming an A1C right at 6.5% is still borderline prediabetes rather than recognizing it as the point where the diabetes range category begins.
- Using A1C values from tests affected by anemia, recent transfusion, or certain hemoglobin variants, which can distort the underlying A1C measurement before this formula is even applied.
Edge Cases to Watch For
- Very low or very high A1C entries still compute a number even though the original ADAG regression wasn't validated across the full range of possible inputs, so extreme values should be interpreted with more caution.
- An A1C of exactly 6.5% is placed in Diabetes range rather than Prediabetes range, since the category check only treats values strictly below 6.5 as prediabetes.
- The tool has a single numeric field, so it cannot account for conditions such as certain anemias, hemoglobin variants, or recent blood loss that are known to make A1C an unreliable proxy for average glucose in some people.
Common Use Cases
- Someone who just received lab results reporting only an A1C percentage and wants to see it expressed as an average glucose number.
- People tracking A1C values across multiple lab visits who want a consistent way to translate each one into eAG.
- Patients discussing glucose targets with a clinician who want to understand how their A1C corresponds to everyday meter readings.