A1C Calculator: Hemoglobin A1C to Average Blood Sugar
Convert your Hemoglobin A1C percentage to estimated average blood sugar (eAG) in both mg/dL and mmol/L for better diabetes management.
Enter your most recent HbA1c result and instantly see your estimated average glucose over the past two to three months, plus what range it falls in.
A1C Calculator: Hemoglobin A1C to Average Blood Sugar
Convert your Hemoglobin A1C percentage to estimated average blood sugar (eAG) in both mg/dL and mmol/L for better diabetes management.
About the A1C calculator
Hemoglobin A1C — also written HbA1c — is a blood test that reflects your average blood sugar over the previous two to three months. It works because glucose in the bloodstream binds to hemoglobin, the oxygen-carrying protein inside red blood cells. The higher your average glucose, the more glycated hemoglobin you accumulate, and since red blood cells live about 120 days, a single A1C reading captures a long-term picture rather than a momentary snapshot. This calculator converts that percentage into an estimated average glucose (eAG) value you can compare directly with your day-to-day meter readings.
The conversion uses the formula adopted from the landmark ADAG study and endorsed by the American Diabetes Association: estimated average glucose in mg/dL equals 28.7 multiplied by your A1C percentage, minus 46.7. To express the same result in the international unit mmol/L, the mg/dL figure is divided by 18.0182. So an A1C of 7% corresponds to roughly 154 mg/dL or 8.6 mmol/L. Reporting both units makes the result useful whether your country uses mg/dL (such as the United States) or mmol/L (such as the UK, Canada, and much of Europe).
Interpreting the number matters as much as calculating it. According to standard diagnostic thresholds, an A1C below 5.7% is considered normal, 5.7% to 6.4% indicates prediabetes, and 6.5% or higher is in the diabetes range. For most adults already living with diabetes, a common management target is below 7%, though your personal goal should be set with your healthcare provider and may be higher or lower depending on age, other conditions, and risk of hypoglycemia. The calculator labels which range your entry falls into so you can see the clinical context at a glance.
Knowing your eAG helps bridge the gap between a lab value and the glucose numbers you see on a meter or continuous glucose monitor every day. If your A1C suggests an average of 154 mg/dL but your fasting readings are consistently lower, the difference may come from post-meal spikes you are not capturing. Tracking eAG over successive A1C tests is one of the clearest ways to see whether changes to diet, activity, or medication are actually moving your long-term control in the right direction.
A few caveats are worth remembering. The eAG formula is a statistical estimate, so an individual's true average can differ from the calculated value. Certain conditions — anemia, recent blood loss or transfusion, pregnancy, kidney disease, and some hemoglobin variants — can make A1C results less reliable. The A1C calculator is for education and self-tracking only and is not a substitute for professional medical advice; always discuss your results and treatment plan with a qualified clinician.
A1C to average blood sugar examples
Click any example button under the calculator to load these A1C values.
| Hemoglobin A1C | Estimated average glucose | Interpretation |
|---|---|---|
| A1C 5% | 96.8 mg/dL (5.4 mmol/L) | A normal result. Average glucose under about 117 mg/dL corresponds to an A1C below 5.7%. |
| A1C 6% | 125.5 mg/dL (7.0 mmol/L) | Falls in the prediabetes range (5.7%–6.4%), a signal to consider lifestyle changes. |
| A1C 7% | 154.2 mg/dL (8.6 mmol/L) | In the diabetes range; 7% is also a common management target for many adults with diabetes. |
| A1C 9% | 211.6 mg/dL (11.7 mmol/L) | Indicates poorly controlled diabetes that usually calls for medical review and treatment changes. |
How to use the A1C calculator
- Find your most recent Hemoglobin A1C percentage from your lab report or doctor.
- Type that percentage into the Hemoglobin A1C field (for example, 7.0).
- Click Calculate Average Blood Sugar to convert it to estimated average glucose.
- Read your eAG in both mg/dL and mmol/L, along with the range it falls into.
- Click Reset to try another value, or load an example to see how different A1C levels compare.
A1C calculator FAQ
What does the A1C test measure?
A1C measures the percentage of your hemoglobin that has glucose attached to it, reflecting your average blood sugar over the past two to three months. Because red blood cells live about 120 days, it gives a long-term view rather than a single-moment reading.
How is A1C converted to average blood sugar?
The calculator uses the ADA-endorsed formula: estimated average glucose (mg/dL) = 28.7 × A1C − 46.7. Dividing the mg/dL result by 18.0182 gives the value in mmol/L. For example, an A1C of 7% equals about 154 mg/dL or 8.6 mmol/L.
What is a normal A1C level?
An A1C below 5.7% is considered normal, 5.7%–6.4% indicates prediabetes, and 6.5% or higher falls in the diabetes range. Many adults with diabetes aim for below 7%, but targets are individual and should be set with a doctor.
Why doesn't my A1C match my daily meter readings?
A1C reflects an average that includes overnight and post-meal periods you may not test. If your meter readings look good but your A1C is high, undetected glucose spikes after meals are a common cause. A continuous glucose monitor can reveal these patterns.
How often should A1C be tested?
Most people with stable, well-controlled diabetes are tested about twice a year, while those changing treatment or not meeting goals may be tested every three months. Your healthcare provider will recommend a schedule based on your situation.
Is this calculator a substitute for medical advice?
No. The eAG value is an educational estimate and certain conditions like anemia, pregnancy, or hemoglobin variants can make A1C less reliable. Always discuss your results and any treatment decisions with a qualified healthcare professional.