A1C to Average Glucose Calculator

Type an HbA1c result as a percentage. The tool converts it to estimated average glucose (eAG) with the equation from the ADAG study (Nathan et al., Diabetes Care 2008):

eAG (mg/dL) = 28.7 × A1C − 46.7

It shows mg/dL rounded to a whole number and mmol/L to one decimal, found by dividing the mg/dL figure by 18.016. The default, 5.7%, gives 28.7 × 5.7 − 46.7 = 116.89, shown as 117 mg/dL and 6.5 mmol/L. The conversion is an estimate, not a diagnosis.

Each step of 1 percentage point in A1C adds 28.7 mg/dL, or about 1.6 mmol/L, to the estimate.

The note under the result uses the American Diabetes Association's A1C ranges (Standards of Care 2026). Some lab reports give A1C in mmol/mol rather than percent, which the tool doesn't show, so both are given here:

These ranges apply to the A1C test itself. The eAG figure the tool shows is only a translation of that result into glucose units, and it has no separate cut-offs of its own.

The equation is a line fitted to data from 507 people (R² = 0.84). It describes the group well, but any one person can sit above or below the line, so your own meter or sensor average can differ from the eAG for your A1C without either being wrong.

If you have a lab A1C at 5.7% or above, or the eAG and your readings disagree by a lot, take both to your doctor. They can interpret the result alongside your history; the calculator can't diagnose or rule anything out.