A1C Calculator (Hemoglobin A1c to Average Blood Sugar)
Use our A1C calculator to convert hemoglobin A1c (HbA1c) to estimated average blood sugar (eAG). Includes the A1C to average blood sugar formula, an A1C and average blood sugar chart (conversion table), and answers about normal A1C range, how often A1C is checked, and why A1C may be high or low.
Hemoglobin A1c and Average Blood Sugar
Hemoglobin A1c (HbA1c or A1C) is a lab test that reflects your average blood sugar over roughly the past 2–3 months.
Estimated average glucose (eAG) converts an A1C percentage into the same units many people see on glucose meters (mg/dL) or in some countries (mmol/L).
This calculator uses the standard A1C→eAG relationship to estimate your average blood sugar from your A1C result.
A1C to Average Blood Sugar Formula
The A1C to eAG conversion uses a linear relationship between A1C (%) and estimated average glucose.
This is an estimate. It won’t capture daily highs/lows—just the overall average.
Use mmol/L if that’s the unit you use for blood glucose.
A quick A1C to average blood sugar conversion.
A1C and Average Blood Sugar Chart
A1C to estimated average glucose (eAG) conversion table.
| A1c (%) | eAG (mg/dL) | eAG (mmol/L) |
|---|---|---|
| 4% | 68 mg/dL | 3.8 mmol/L |
| 4.5% | 82 mg/dL | 4.6 mmol/L |
| 5% | 97 mg/dL | 5.4 mmol/L |
| 5.5% | 111 mg/dL | 6.2 mmol/L |
| 5.7% | 117 mg/dL | 6.5 mmol/L |
| 6% | 126 mg/dL | 7 mmol/L |
| 6.5% | 140 mg/dL | 7.8 mmol/L |
| 7% | 154 mg/dL | 8.6 mmol/L |
| 7.5% | 169 mg/dL | 9.4 mmol/L |
| 8% | 183 mg/dL | 10.1 mmol/L |
| 8.5% | 197 mg/dL | 10.9 mmol/L |
| 9% | 212 mg/dL | 11.8 mmol/L |
| 9.5% | 226 mg/dL | 12.6 mmol/L |
| 10% | 240 mg/dL | 13.4 mmol/L |
| 11% | 269 mg/dL | 14.9 mmol/L |
| 12% | 298 mg/dL | 16.5 mmol/L |
Values are estimates using the standard A1C→eAG conversion.
How to Convert A1C to Average Blood Sugar
- 1
Enter your A1C value (%).
- 2
The calculator converts it to eAG in mg/dL using eAG = 28.7×A1C − 46.7.
- 3
It also converts mg/dL to mmol/L by dividing by 18.
- 4
Use the chart to quickly compare common A1C values to average blood sugar.
Frequently Asked Questions
Common diagnostic ranges are: below 5.7% (normal), 5.7% to 6.4% (prediabetes), and 6.5% or higher (diabetes). Your clinician interprets results in context.
A higher A1C generally means your average blood sugar has been higher over the past couple of months. Causes can include insufficient diabetes control, medication changes, diet/activity changes, illness, and other factors.
Yes. A low A1C can reflect consistently lower blood glucose, but it can also happen when something affects red blood cell lifespan/turnover (which can make A1C less reliable). If your A1C seems unexpectedly low, discuss it with a clinician.
How often you’re tested depends on your situation. Many people with diabetes get A1C checked at least twice a year when stable, and more often (such as every ~3 months) if treatment changes or goals aren’t being met.
Because the conversion gives an overall average and may not match your meter/CGM exactly. Individual biology and glucose variability (spikes/lows) can make the estimate differ from day-to-day readings.
Targets can vary by age and health factors and should be individualized. If you’re using A1C goals for diabetes management, it’s best to follow a plan set with your care team.
Many people can reduce A1C with an appropriate treatment plan. Because this is medical and highly individualized, talk with a clinician about safe next steps.