A1c Converter (eAG)
Convert hemoglobin A1c to estimated average glucose (eAG) in mg/dL or mmol/L — and back — using the ADA's published formula.
Patients understand glucose numbers; A1c percentages are abstract. The estimated average glucose (eAG) translates an A1c result into the same units as a home glucose meter, using the regression formula from the international A1c-Derived Average Glucose (ADAG) study that the American Diabetes Association publishes: eAG (mg/dL) = 28.7 × A1c − 46.7. Convert in either direction below.
A1c to estimated average glucose
Average glucose to estimated A1c
Reference table (ADA formula)
| A1c (%) | eAG (mg/dL) | eAG (mmol/L) |
|---|---|---|
| 5.5 | 111 | 6.2 |
| 6.0 | 126 | 7.0 |
| 6.5 | 140 | 7.8 |
| 7.0 | 154 | 8.6 |
| 7.5 | 169 | 9.4 |
| 8.0 | 183 | 10.2 |
| 9.0 | 212 | 11.8 |
| 10.0 | 240 | 13.3 |
The formula comes from the ADAG study (Nathan et al., Diabetes Care 2008), which regressed A1c against thousands of continuous and self-monitored glucose readings; the ADA publishes it in its Standards of Care and many laboratories now report eAG alongside A1c. Two cautions. First, eAG is an average of averages — two patients with the same A1c can have very different daily patterns and hypoglycemia exposure. Second, anything that changes red-blood-cell lifespan or hemoglobin — anemia and its treatment, transfusion, hemoglobinopathies, pregnancy, advanced kidney disease — can pull the laboratory A1c away from the true average glucose in either direction, and CGM-derived metrics (such as the glucose management indicator) may describe the patient better. For diabetes practices, the A1c value also anchors quality reporting and risk documentation; our endocrinology billing workflow checks that the documented A1c and the diabetes control diagnosis tell the same story.
Disclaimer: This converter is educational only and is not medical advice. It applies the ADA's published population formula; it does not replace laboratory testing or clinical judgment, and individual results vary.
Frequently asked questions
What is the formula to convert A1c to average glucose?
The ADA's published formula from the ADAG study: eAG in mg/dL = 28.7 × A1c − 46.7. To express the result in mmol/L, divide mg/dL by 18. The reverse — estimating A1c from average glucose — is A1c = (eAG + 46.7) ÷ 28.7.
Why does my patient's A1c not match their meter or CGM average?
The formula is a population average, and A1c depends on red-blood-cell lifespan and hemoglobin as well as glucose. Anemia, recent transfusion, hemoglobin variants, pregnancy, and kidney disease can all shift A1c away from the true glucose average. Meter averages also sample only the moments tested, unlike the full 2–3 month exposure A1c reflects.
Is eAG the same as the glucose management indicator (GMI)?
No. eAG is estimated from A1c using the ADAG regression. GMI is estimated from CGM mean glucose using a different formula (GMI % = 3.31 + 0.02392 × mean glucose in mg/dL). They often differ for the same patient, which is why the CGM metric was renamed from "estimated A1c" to GMI.