A1C to eAG Calculator
Convert an A1C percentage into estimated average glucose (eAG), shown in mg/dL and mmol/L at the same time. eAG expresses a lab A1C result in the same units your meter or CGM uses day to day.
Convert
Enter your A1C percentage
Type your A1C to one decimal place (for example 7.0); both eAG values update as you type.
eAG in mg/dL
Enter an A1C value above to see the mg/dL estimate.
eAG in mmol/L
Enter an A1C value above to see the mmol/L estimate.
The formula
The ADAG formula, and where it comes from
eAG (mg/dL) = 28.7 × A1C − 46.7
eAG (mmol/L) = 1.59 × A1C − 2.59
Both equations come from the A1C-Derived Average Glucose (ADAG) study (Nathan et al., Diabetes Care 2008), which correlated frequent glucose measurements with laboratory A1C results. The name “ADAG formula” applies only to this forward direction — turning an A1C percentage into an estimated average glucose. Estimating in the reverse direction is an algebraic rearrangement, not part of the published ADAG regression.
Where the estimate is reliable
The ADAG study enrolled 507 participants, each contributing roughly 2,700 glucose measurements over three months. The scatter around the regression line is real: the reported standard deviation is about 15.7 mg/dL, so two people with the same A1C can have noticeably different true averages. The relationship is most reliable for A1C values between 4% and 10%, and it is not suitable during pregnancy, with hemoglobin variants, or with anemia and other conditions that change red blood cell turnover.
Reference
ADA reference ranges — education only
The American Diabetes Association publishes these A1C ranges as population-level reference points. They are reproduced here for education only.
| A1C result | ADA category |
|---|---|
| Below 5.7% | Normal |
| 5.7% – 6.4% | Prediabetes |
| 6.5% or above | Diabetes |
This page never compares your input against this table and never labels your result with one of these categories: diagnosis requires an NGSP-certified laboratory test interpreted by a clinician, not a calculator.
FAQ
A1C and eAG questions
What does eAG actually represent?
Estimated average glucose (eAG) translates an A1C percentage into the mg/dL or mmol/L units that meters and CGMs report, using the regression from the ADAG study (Nathan et al., Diabetes Care 2008). It is a statistical estimate of your average glucose over roughly the past three months — not a replacement for the averages your own meter or CGM computes, which can differ because A1C weights recent weeks more heavily and red blood cell lifespan varies between people.
Why doesn't this page tell me whether my A1C is normal, prediabetes, or diabetes?
Attaching one of those labels to your number would be a diagnostic judgment, and the American Diabetes Association requires diagnosis to be based on laboratory testing with an NGSP-certified method, interpreted by a clinician — not on a value typed into a web calculator. The ADA reference table on this page is educational background only: the calculator never compares your input against it and never highlights which row your value would fall in.
How accurate is the eAG estimate?
The ADAG study derived the formula from about 2,700 glucose measurements per participant across 507 people, and the scatter around the regression line is meaningful: the reported standard deviation is roughly 15.7 mg/dL. The relationship is most reliable for A1C values between 4% and 10%, and it does not hold well during pregnancy, with hemoglobin variants, or with anemia and other conditions that change red blood cell turnover.