A1C Calculator
Convert between A1C percentage and estimated average glucose (eAG). A1C reflects average blood sugar over the past 3 months.
⚠️ For educational use. Consult your doctor for diabetes management decisions. This calculator does not diagnose or treat any condition.
Reviewed & updated for 2026 by Rakesh Choudhary, PhDMethodology & sources · How we calculate
A1C to glucose reference
| A1C | eAG (mg/dL) | eAG (mmol/L) | Status |
|---|---|---|---|
| 5.0% | 97 | 5.4 | Normal |
| 5.7% | 117 | 6.5 | Prediabetes range |
| 6.0% | 126 | 7.0 | Prediabetes range |
| 6.5% | 140 | 7.8 | Diabetes range |
| 7.0% | 154 | 8.6 | Diabetes range |
| 8.0% | 183 | 10.2 | Diabetes range |
| 9.0% | 212 | 11.8 | Diabetes range |
| 10.0% | 240 | 13.4 | Diabetes range |
eAG from the ADAG formula (Nathan et al., Diabetes Care 2008); mmol/L is mg/dL ÷ 18. Status is the diagnostic range from NIDDK. CDC puts the goal for most people with diabetes at 7% or less; your doctor sets yours.
What A1C is actually measuring
Hemoglobin in red blood cells binds with glucose in the bloodstream. The more glucose is present over time, the higher the percentage of hemoglobin molecules that get "glycated." A1C measures that percentage, which is why it reflects your average blood sugar over the past 3 months (NIDDK) rather than a single moment.
That makes it a different measurement from a finger-stick test (one moment) or a fasting glucose test (one fasted moment). You don't have to fast before an A1C test, and cutting carbs for a few days beforehand does not undo the months of glucose it already reflects.
The formula used here, eAG = 28.7 × A1C − 46.7, comes from the ADAG study (Nathan et al., Diabetes Care 2008), which compared A1C with measured average glucose in 507 participants. It is a population average: the study's own table puts the 95% range around a 7% A1C at 123 to 185 mg/dL, so one person's true average can sit well away from the estimate.
A1C targets are personalized, not one-size-fits-all
CDC says that for most people with diabetes the A1C goal is 7% or less, and that your doctor will set your specific goal based on your full medical history. NIDDK puts it the same way: people have different A1C targets depending on their diabetes history and general health, and you should agree yours with your health care professional.
This calculator shows the diagnostic range an A1C falls in, not whether it meets your goal.
When A1C lies, and what to use instead
CDC and NIDDK list conditions that can make an A1C result misleading:
- Blood disorders: sickle cell anemia (or sickle cell disease), thalassemia and other hemoglobin variants.
- Blood loss or transfusion: both can change A1C levels.
- Anemia: severe anemia can affect the result, and iron-deficiency anemia can give a falsely high A1C.
- Kidney failure and hemodialysis, liver disease, erythropoietin treatment and certain other medicines.
- Pregnancy: CDC names early and late pregnancy.
If any of these apply, or your A1C doesn't match your home readings, ask your doctor which other glucose test suits you. Sources: CDC, A1C Test for Diabetes and Prediabetes; NIDDK, The A1C Test & Diabetes.
FAQs
What is A1C?
A1C (also called HbA1c or glycated hemoglobin) is a blood test that reflects your average blood glucose over the past 3 months, according to the NIDDK. It's expressed as a percentage of hemoglobin that has glucose attached. You don't have to fast before the test.
What's a normal A1C?
Below 5.7% is normal, 5.7% to 6.4% is prediabetes and 6.5% or above is diabetes (NIDDK and CDC). Many people with diabetes aim for 7% or less, but the right target is one your doctor sets for you.
How is A1C converted to average blood sugar?
With the ADAG study's formula: eAG (mg/dL) = 28.7 × A1C − 46.7. Example: an A1C of 7.0% gives 28.7 × 7.0 − 46.7 = 154 mg/dL. For mmol/L, divide the mg/dL figure by 18: 154 mg/dL is about 8.6 mmol/L, the value in the study's own table.
How often should I test A1C?
CDC says most people with diabetes have their A1C tested at least twice a year. With prediabetes, your doctor will likely recommend repeating it every 1 to 2 years. With a normal result, your doctor sets a retesting schedule based on your age and risk factors.
Can A1C be wrong?
Yes. CDC lists severe anemia, kidney failure, liver disease, blood disorders such as sickle cell anemia or thalassemia, certain medicines, blood loss or transfusions, and early or late pregnancy as things that can affect the result. NIDDK adds that iron-deficiency anemia can give a falsely high A1C. If your A1C and your home readings disagree, ask your doctor whether another test would suit you better.