To convert A1C to glucose, use the American Diabetes Association formula: estimated average glucose (mg/dL) = 28.7 × A1C − 46.7. An A1C of 7%, for example, works out to an average blood glucose of about 154 mg/dL over the prior 2 to 3 months.
The A1C-to-Glucose Formula
A1C is a percentage, but blood sugar meters report milligrams per deciliter (mg/dL) or millimoles per liter (mmol/L). The gap between those units is why so many people struggle to interpret their lab result.
The ADA adopted two conversion equations from the 2008 A1C-Derived Average Glucose (ADAG) study. Both produce a single number called estimated average glucose, or eAG.
- mg/dL: eAG = 28.7 × A1C − 46.7
- mmol/L: eAG = 1.59 × A1C − 2.59
Plug any A1C percentage in and you get a usable average. The formula is linear, so each 1% rise in A1C adds roughly 28.7 mg/dL to the average. For a broader explanation of the hemoglobin math, see our A1C levels guide.
Worked Examples
Three step-by-step conversions make the formula concrete.
Example 1: A1C of 5.7%
28.7 × 5.7 = 163.59. Subtract 46.7 to get 116.9 mg/dL. An A1C of 5.7% sits at the low end of prediabetes, matching an average glucose just above the 100 mg/dL fasting cutoff.
Example 2: A1C of 6.5%
28.7 × 6.5 = 186.55. Subtract 46.7 to get 139.85 mg/dL. This is the diagnostic threshold for type 2 diabetes, and the average already runs about 40 mg/dL above a healthy target.
Example 3: A1C of 8.0%
28.7 × 8.0 = 229.6. Subtract 46.7 to get 182.9 mg/dL. That is the kind of average glucose that drives long-term complications in eyes, kidneys, and nerves.
Full A1C to Glucose Conversion Table
The table below uses the ADA formula for every A1C from 4% to 14%. Round your lab result up or down and read across.
| A1C (%) | eAG (mg/dL) | eAG (mmol/L) | Category |
|---|---|---|---|
| 4.0 | 68 | 3.8 | Below normal range |
| 4.5 | 82 | 4.6 | Normal |
| 5.0 | 97 | 5.4 | Normal |
| 5.3 | 105 | 5.9 | Normal |
| 5.5 | 111 | 6.2 | Normal |
| 5.7 | 117 | 6.5 | Prediabetes |
| 6.0 | 126 | 7.0 | Prediabetes |
| 6.2 | 131 | 7.3 | Prediabetes |
| 6.4 | 137 | 7.6 | Prediabetes |
| 6.5 | 140 | 7.8 | Diabetes |
| 7.0 | 154 | 8.6 | Diabetes |
| 7.5 | 169 | 9.4 | Diabetes |
| 8.0 | 183 | 10.2 | Diabetes |
| 9.0 | 212 | 11.8 | Diabetes, high risk |
| 10.0 | 240 | 13.4 | Diabetes, high risk |
| 11.0 | 269 | 14.9 | Very high |
| 12.0 | 298 | 16.5 | Very high |
| 14.0 | 355 | 19.7 | Severely elevated |
Why A1C Represents Two to Three Months
Glucose attaches permanently to hemoglobin inside red blood cells. Because those cells circulate for about 120 days before the spleen recycles them, any single A1C test is a weighted average of glucose exposure across the entire lifespan of the cells currently in your bloodstream.
That average is weighted toward recent weeks. Roughly 50% of an A1C reflects the most recent 30 days, 25% reflects days 30 to 60, and 25% reflects days 60 to 120, according to American Diabetes Association guidance. Changes you make today will show up fastest on your next test.
Why Your Meter Average Will Not Match
Many people check A1C after seeing a low 7-day meter average and feel confused when the lab number looks higher. Three factors explain the mismatch.
- Sampling bias. Most people test before meals, missing the post-meal peaks that drive A1C upward.
- Night hours. You do not fingerstick at 3 a.m., but your glucose is still there.
- Biological variation. Red blood cell turnover and hemoglobin variants shift A1C up or down 0.3% in either direction for the same true average.
A continuous glucose monitor (CGM) sidesteps this by measuring every 5 minutes. The glucose management indicator (GMI) it produces typically lands within 0.3% of a lab A1C.
Convert Faster With Our Calculator
If doing arithmetic on paper is not your idea of fun, our A1C calculator applies the formula instantly. You can also view the side-by-side reference in our A1C vs glucose chart, which includes goal ranges for adults with and without diabetes.
What Counts as a Good Target
For most nonpregnant adults with diabetes, the ADA Standards of Care recommend an A1C below 7%, which equals about 154 mg/dL average glucose. Older adults or those with limited life expectancy may target 7.5% to 8% to reduce hypoglycemia risk, while younger adults without complications sometimes aim below 6.5%.
| Goal | A1C target | Average glucose |
|---|---|---|
| Nondiabetic reference | Below 5.7% | Below 117 mg/dL |
| Standard diabetes goal | Below 7.0% | Below 154 mg/dL |
| Stricter goal | Below 6.5% | Below 140 mg/dL |
| Relaxed goal (older adults) | Below 8.0% | Below 183 mg/dL |
The Bottom Line
A1C and average glucose are two views of the same thing. Multiply your A1C by 28.7 and subtract 46.7 to turn a lab percentage into a mg/dL average you can relate to your meter. Use the conversion as a reality check on your daily readings, not a replacement for them, and review trends with your clinician to set a personal A1C goal.
