This A1C to average blood sugar guide explains how to convert an A1C result into estimated average glucose (eAG), includes a practical blood sugar conversion chart, and shows why the estimate may not match individual meter or continuous glucose monitor readings.
Overview
A1C is a laboratory measurement that reflects the percentage of hemoglobin with glucose attached to it. Because red blood cells circulate for several months, A1C provides a longer-term view of blood sugar than a single finger-stick or sensor reading. It is commonly used to assess blood sugar control and to help clinicians evaluate diabetes or prediabetes alongside other information.
Estimated average glucose, or eAG, translates an A1C percentage into the units used by most home glucose meters. This can make an A1C result easier to understand. However, eAG is an estimate of an average—not a prediction of what your blood sugar should be at a particular moment and not a replacement for your care plan.
Use the following chart as a reference:
| A1C | Estimated average glucose (mg/dL) | Estimated average glucose (mmol/L) |
|---|---|---|
| 4% | 68 | 3.8 |
| 5% | 97 | 5.4 |
| 6% | 126 | 7.0 |
| 7% | 154 | 8.6 |
| 8% | 183 | 10.2 |
| 9% | 212 | 11.8 |
| 10% | 240 | 13.4 |
| 11% | 269 | 14.9 |
| 12% | 298 | 16.5 |
These values are rounded. A1C goals are personal and may differ according to age, pregnancy, diabetes type, medications, other health conditions, risk of low blood sugar, and treatment preferences. Do not change insulin or other medication based on this chart alone.
How to estimate
To convert A1C to estimated average glucose in milligrams per deciliter (mg/dL), use this calculator-style formula:
eAG (mg/dL) = 28.7 × A1C − 46.7
For millimoles per liter (mmol/L), use:
eAG (mmol/L) = 1.59 × A1C − 2.59
Enter the A1C as a number, not as a decimal. For example, an A1C of 7.2 is entered as 7.2. The formulas produce an approximate average and should be rounded to a practical whole number in mg/dL or one decimal place in mmol/L.
If you prefer to convert between glucose units, divide mg/dL by 18 to approximate mmol/L. To convert mmol/L to mg/dL, multiply by 18. Because both A1C and glucose measurements have normal biological and measurement variation, small differences between a formula result and a displayed chart value are expected.
For a more detailed reference, see A1C to Average Blood Sugar Chart and Calculator: How to Convert Your Results.
Inputs and assumptions
The main input is a laboratory A1C result reported as a percentage. The conversion assumes the result reasonably represents your average glucose over the period measured. It does not account for the timing of meals, exercise, medication doses, sleep, illness, stress, or daily glucose swings.
This distinction matters. Two people can have the same A1C and different patterns: one may have relatively stable readings, while another may alternate between high and low blood sugar. An A1C also does not show whether glucose is highest before breakfast, after meals, overnight, or during exercise. A meter log or continuous glucose monitor can add this information.
The relationship between A1C and eAG may be less reliable when red blood cells do not have a typical lifespan or when a health condition affects hemoglobin. Examples may include some forms of anemia, recent blood loss or transfusion, certain hemoglobin variants, kidney disease, pregnancy, or treatment that changes red blood cell production. If your A1C seems inconsistent with your home readings or symptoms, ask your clinician whether another test or a different way of monitoring would be useful.
Home meters and continuous glucose monitors also measure glucose differently and at different times. A meter reading is a point-in-time result, while a sensor may measure glucose in interstitial fluid and can lag behind blood glucose during rapid changes. Compare patterns over time rather than treating one reading as proof that the A1C estimate is wrong.
Worked examples
Example 1: A1C of 6.5%
Using the mg/dL formula: 28.7 × 6.5 − 46.7 = approximately 140 mg/dL. Using the mmol/L formula gives approximately 7.8 mmol/L. This is an estimated average, not a fasting or after-meal target.
Example 2: A1C of 7.2%
28.7 × 7.2 − 46.7 = approximately 160 mg/dL, or about 8.9 mmol/L. If your meter usually shows readings near this level, the results may appear broadly consistent. If it shows a very different pattern, record when the readings occur and discuss the comparison at your next appointment.
Example 3: A1C of 8.4%
28.7 × 8.4 − 46.7 = approximately 194 mg/dL, or about 10.8 mmol/L. This number does not identify the cause of high blood sugar. Possible contributors include medication timing, missed doses, changes in food intake or activity, illness, stress, or changes in insulin production. Your diabetes care team can help interpret the result in context.
When reviewing an A1C, write down the result, test date, recent glucose patterns, medication changes, and any episodes of low blood sugar. This creates a more useful discussion than focusing on the conversion alone.
When to recalculate
Recalculate whenever you receive a new A1C result, especially after a treatment change or a sustained change in meals, activity, weight, illness, or daily glucose patterns. Keeping a dated record makes it easier to compare results over time. A practical log might include:
- A1C result and laboratory date
- Calculated eAG in your preferred glucose units
- Typical fasting, before-meal, and after-meal readings, if available
- Recent medication, insulin, or device changes
- Questions about symptoms, low readings, or readings that do not match the A1C
Bring this record to your next appointment and ask how your personal A1C goal was selected. Ask whether your readings suggest highs or lows that an A1C is hiding, and whether anemia, kidney problems, pregnancy, or another condition could affect interpretation. Seek prompt medical advice for severe or persistent high blood sugar, repeated low readings, vomiting, dehydration, confusion, or trouble breathing. Use this chart to organize information—not to diagnose yourself or make medication changes without guidance.
