eAG/A1C Calculator

A1C reflects your average blood glucose over roughly the past three months, but it’s reported as a percentage, not in the units your glucose meter uses. eAG (estimated average glucose) translates that percentage into mg/dL or mmol/L, so a lab result and day-to-day readings can be compared directly, in either direction.

What This Calculator Measures

eAG is not a separate lab value. It’s a conversion of A1C into glucose units using a formula derived from real-world monitoring data, making the same 3-month average easier to read alongside daily glucose numbers, and just as easily converted back the other way.

The Formula

This calculator uses the ADAG (A1C-Derived Average Glucose) equation, which paired frequent glucose monitoring with A1C tests across roughly 500 participants and found a strong, consistent linear relationship between the two¹.

eAG (mg/dL) = 28.7 × A1C − 46.7

A1C (%) = (eAG in mg/dL + 46.7) ÷ 28.7

How This Calculator Computes Your Result

Choose a direction, A1C to eAG or eAG to A1C, enter your value, and pick mg/dL or mmol/L if you’re working with eAG. For mmol/L, we convert to mg/dL internally (dividing by 18.0182), run the formula, then convert back and round to 1 decimal place for display. mg/dL results are rounded to the nearest whole number.

What Your Result Means

These thresholds come from the American Diabetes Association’s Standards of Care². If your entered or computed A1C falls below about 4% or above about 15% (or eAG below 65 or above 380 mg/dL), the result is well outside the data behind the ADAG formula, and the calculator will flag it rather than show a falsely precise number. Most ADAG samples (98.5%) had an A1C between 4% and 10%, so estimates at higher values are less certain¹.

A1C to eAG Reference Chart

For a quick look without entering a number, here’s how common A1C values translate to eAG at both units.

Values are calculated directly from the formula above and rounded for display. Use the calculator itself for any A1C not shown here.

Why the Numbers May Not Match Your Monitor

A1C is a weighted average that leans more heavily on your most recent few weeks. It can also run higher or lower than your true average glucose if you have anemia, a hemoglobin variant such as sickle cell trait, chronic kidney disease, or are pregnant, conditions the current Standards of Care specifically flag as limiting A1C’s accuracy independent of glucose levels².

Even without any of these conditions, research has found that normal person-to-person variation in how long red blood cells live is, on its own, enough to shift A1C somewhat above or below what a person’s actual average glucose would predict³. This tool is a lab-value translator, not a diagnostic tool, and A1C category thresholds should be confirmed with a healthcare provider.