How do you convert A1c to average glucose?

Estimated average glucose in mg/dL equals 28.7 times your A1c percent minus 46.7, from the ADAG study. Divide mg/dL by 18 to get mmol/L.

What A1c means diabetes?

By ADA criteria, an A1c below 5.7% is normal, 5.7–6.4% is prediabetes, and 6.5% or higher on two tests indicates diabetes. Diagnosis is a clinician decision, not a single number.

A1c to Glucose Converter — eAG in mg/dL & mmol/L

Convert either way

HbA1c

Estimated avg glucose

mg/dL

Glucose units

Estimated average glucose

114 mg/dL

Normal

A1c5.6%

eAG (mg/dL)114 mg/dL

eAG (mmol/L)6.3 mmol/L

Categories follow ADA criteria (normal <5.7%, prediabetes 5.7–6.4%, diabetes ≥6.5%). A diagnosis requires clinician confirmation, usually on repeat testing. This tool is educational, not diagnostic.

How this works

Methodology reviewed July 2026

This converter translates an HbA1c percentage into an estimated average glucose (eAG) and back, using the linear relationship established by the ADAG study. It works in both directions — edit the A1c and the eAG updates, or edit the eAG and the A1c updates — and shows the result in both mg/dL and mmol/L with ADA category context (normal, prediabetes, diabetes).

Formula

eAG (mg/dL) = 28.7 × A1c(%) − 46.7        (ADAG regression)
A1c (%)     = (eAG[mg/dL] + 46.7) / 28.7  (inverse)
mmol/L      = mg/dL ÷ 18.0182
ADA bands: normal <5.7% · prediabetes 5.7–6.4% · diabetes ≥6.5%

Inputs

HbA1c percent · or estimated average glucose · Glucose units (mg/dL / mmol/L)

Outputs

Estimated average glucose (mg/dL and mmol/L) · Back-calculated A1c · ADA category band

Assumptions

The ADAG regression relating A1c to average glucose holds for the individual.
Red-blood-cell lifespan and hemoglobin are normal, so A1c reflects true average glucose.
The mg/dL to mmol/L conversion uses the standard divisor of 18.0182.

Limitations

eAG is a population average — a true average glucose can differ from the estimate.
A1c is skewed by anemia, recent blood loss, pregnancy, and some hemoglobin variants.
It is a trend and education tool, not a glucometer or a diagnostic instrument.

Safety

ADA categories are context, not a diagnosis — diabetes is confirmed by a clinician, usually on repeat testing.
Do not adjust medication based on a converted value; discuss results with your care team.

References

Nathan DM et al. Translating the A1C Assay Into Estimated Average Glucose Values (ADAG). Diabetes Care (2008)

This calculator is for educational purposes only and is not medical advice, diagnosis, or treatment. Results are estimates based on published formulas and population averages — your individual values may differ. Nothing here is calculated on a server: everything runs in your browser and no data is stored or sent anywhere. Always consult a qualified clinician before making health, medication, or training decisions.