What Is the HbA1c to Average Glucose Calculator?
This tool converts a glycated hemoglobin (HbA1c) percentage into an estimated average glucose (eAG) level, expressed in both mg/dL and mmol/L. HbA1c reflects your average blood sugar over the previous 2–3 months, while eAG translates that percentage into the more familiar daily glucose meter units. This is a universal medical conversion based on the international ADAG (A1c-Derived Average Glucose) study and is not specific to any country.
How to Use It
Enter your HbA1c value as a percentage (for example, 7 for 7%). The calculator instantly returns your estimated average glucose in mg/dL and the equivalent in mmol/L. Typical HbA1c values range from about 4% (normal) up to 14% or higher in poorly controlled diabetes.
The Formula Explained
The conversion uses the linear regression derived from the ADAG study:
$$\text{eAG}_{\text{mg/dL}} = 28.7 \times \text{HbA1c (\%)} - 46.7$$To express the result in mmol/L, divide the mg/dL value by 18, since \(1\ \text{mmol/L} \approx 18\ \text{mg/dL}\) of glucose.
$$\text{eAG}_{\text{mmol/L}} = \frac{28.7 \times \text{HbA1c (\%)} - 46.7}{18}$$
Worked Example
Suppose your HbA1c is 7%. Then \(\text{eAG} = 28.7 \times 7 - 46.7 = 200.9 - 46.7 = 154.2\ \text{mg/dL}\). Dividing by 18 gives about \(8.57\ \text{mmol/L}\). So an HbA1c of 7% corresponds to an average glucose of roughly 154 mg/dL (8.6 mmol/L).
FAQ
Is eAG the same as a single glucose reading? No. eAG is an estimate of your average glucose over months, not your current reading at any moment.
Why does my meter average differ from eAG? Meter averages depend on when you test. eAG estimates a true 24-hour average across all times of day, so the two can differ.
Can I rely on this for diagnosis? This calculator is for educational purposes only. Always consult a healthcare professional for diagnosis and treatment decisions.
