This A1C-to-average-blood-sugar guide includes a simple calculator, a practical A1C chart, worked examples, and a tracking worksheet. Use it to understand what an A1C result may mean over time—but not to replace your clinician’s interpretation or your personal blood sugar targets.
Overview
A1C, also called hemoglobin A1C or HbA1c, is a blood test that estimates your average blood glucose over roughly the previous two to three months. It does not show every high or low, and it gives more weight to the most recent weeks. A home glucose meter or continuous glucose monitor, by contrast, shows individual readings and patterns throughout the day.
The term estimated average glucose (eAG) converts an A1C percentage into an approximate average blood sugar value. The result is usually expressed in milligrams per deciliter (mg/dL), with an optional conversion to millimoles per liter (mmol/L).
For general interpretation, an A1C below 5.7% is commonly considered in the usual range, 5.7% to 6.4% is commonly used to identify prediabetes, and 6.5% or higher may indicate diabetes. A diagnosis generally requires appropriate testing and confirmation, especially when a person has no clear symptoms. Treatment goals are individualized; a “normal” result is not automatically the correct target for every person with diabetes.
A1C to average blood sugar chart
| A1C | Estimated average glucose | Approximate mmol/L |
|---|---|---|
| 5.0% | 97 mg/dL | 5.4 |
| 5.5% | 111 mg/dL | 6.2 |
| 5.7% | 117 mg/dL | 6.5 |
| 6.0% | 126 mg/dL | 7.0 |
| 6.5% | 140 mg/dL | 7.8 |
| 7.0% | 154 mg/dL | 8.6 |
| 7.5% | 169 mg/dL | 9.4 |
| 8.0% | 183 mg/dL | 10.2 |
| 8.5% | 197 mg/dL | 10.9 |
| 9.0% | 212 mg/dL | 11.8 |
| 10.0% | 240 mg/dL | 13.3 |
| 11.0% | 269 mg/dL | 14.9 |
| 12.0% | 298 mg/dL | 16.5 |
Values are rounded estimates, not a promise that your meter or sensor will show the same average. Two people with the same A1C can have very different patterns of fasting, after-meal, and overnight blood sugar.
How to estimate
To convert A1C to eAG in mg/dL, use this formula:
eAG (mg/dL) = 28.7 × A1C − 46.7
For mmol/L, use:
eAG (mmol/L) = 1.59 × A1C − 2.59
To use the calculator, enter the A1C as a percentage—not as a decimal. For example, enter 7.2 rather than 0.072. Multiply the A1C by 28.7, subtract 46.7, and round the result to a whole number if desired.
You can also estimate the A1C associated with an average glucose reading by reversing the calculation:
A1C (%) = [eAG (mg/dL) + 46.7] ÷ 28.7
This reverse calculation is useful when reviewing a meter or continuous glucose monitor summary, but the displayed average may be affected by missing readings, sensor wear time, or testing at only certain times of day.
Inputs and assumptions
The calculation uses one input: your laboratory or clinician-reported A1C percentage. It assumes the standard relationship between A1C and average glucose applies reasonably well to you. That relationship is an estimate, so it should be used for context rather than for changing insulin, medication, food, or exercise plans on your own.
An A1C result may not reflect your usual blood sugar accurately in some situations. Ask your healthcare professional how to interpret it if you have anemia, recent blood loss or transfusion, kidney or liver disease, a hemoglobin variant, or another condition that changes red blood cell life span. Pregnancy also uses different monitoring goals and may require additional testing; do not apply this chart to gestational diabetes decisions without clinical guidance.
Timing matters, too. A1C is a longer-term measure, while a finger-stick or sensor reading is a moment-specific measurement. A person may have an acceptable average but frequent highs and lows, or a higher average with relatively steady readings. Review both the number and the pattern.
When comparing results, record the test date, A1C, eAG, medication changes, illness, major changes in activity, and any issues that could affect testing. Keeping these details together makes an appointment discussion more useful.
Worked examples
Example 1: A1C of 6.8%
Using the formula: 28.7 × 6.8 − 46.7 = approximately 148 mg/dL, or about 8.2 mmol/L. This is an estimated average, not a recommended target. Your clinician may set a different goal based on age, diabetes type, medications, complications, pregnancy status, and the risk of low blood sugar.
Example 2: A1C of 8.2%
28.7 × 8.2 − 46.7 = approximately 189 mg/dL, or about 10.5 mmol/L. If your meter average is much lower or higher, discuss the difference rather than assuming one result is wrong. The timing and frequency of meter checks may not capture every part of the day.
Simple tracking worksheet
Copy this table into a notebook or digital document:
| Date | A1C | eAG | Meter or CGM average | Notes |
|---|---|---|---|---|
| ____ | ____% | ____ mg/dL | ____ | Medication, illness, activity, or other context |
| ____ | ____% | ____ mg/dL | ____ | Medication, illness, activity, or other context |
| ____ | ____% | ____ mg/dL | ____ | Medication, illness, activity, or other context |
Bring the completed record to your next appointment. It can help identify whether a change in blood sugar control is related to meals, missed doses, illness, stress, sleep, activity, or a treatment change.
When to recalculate
Recalculate whenever you receive a new A1C, generally at the interval recommended by your healthcare team. Revisit the chart after a medication change, a sustained change in meals or activity, a significant illness, or a major change in weight. The point is to compare trends—not to react to a single value.
Before making changes, look for questions the numbers can help answer: Is the average improving? Are fasting readings high while after-meal readings are closer to target? Are there unexplained lows? Does the A1C seem inconsistent with meter or sensor results? Write these questions down for your clinician.
Seek prompt medical advice for persistent high readings, repeated low readings, or symptoms such as vomiting, confusion, severe weakness, trouble breathing, or inability to keep fluids down. People using insulin or medicines that can cause hypoglycemia should follow their individualized sick-day and low-blood-sugar plan. This A1C calculator is a tracking aid, not an emergency tool and not a substitute for personalized diabetes management.
