Enter your average blood glucose (in mg/dL or mmol/L), your A1C percentage, or a set of recent glucose readings to estimate the other value and see where it falls on the standard A1C scale.
Related Calculators
Formula
The calculator uses the ADAG (A1C-Derived Average Glucose) equation from Nathan et al., 2008.
A1C (%) = (eAG + 46.7) / 28.7
eAG (mg/dL) = 28.7 × A1C − 46.7
where eAG = estimated average glucose in mg/dL, A1C = glycated hemoglobin percentage.
Unit conversion:
mg/dL = mmol/L × 18.0182
mmol/L = mg/dL ÷ 18.0182
Interpretation
The A1C result reflects your average blood glucose over roughly the past 2–3 months, based on how much glucose has attached to hemoglobin in your red blood cells. Use the categories below (American Diabetes Association thresholds):
- Below 5.7% — Normal (eAG under ~117 mg/dL)
- 5.7% – 6.4% — Prediabetes (eAG ~117–137 mg/dL)
- 6.5% and above — Diabetes range (eAG ~140 mg/dL and higher)
- 7.0% — Common treatment target for many adults with diabetes (eAG ~154 mg/dL)
The eAG is a statistical estimate, not a lab measurement. Your actual A1C from a blood draw can differ by several tenths of a percent due to variations in red blood cell lifespan, hemoglobin variants, anemia, pregnancy, and recent transfusions.
A1C to eAG Reference Table
| A1C (%) | eAG (mg/dL) | eAG (mmol/L) |
|---|---|---|
| 5.0 | 97 | 5.4 |
| 5.7 | 117 | 6.5 |
| 6.0 | 126 | 7.0 |
| 6.5 | 140 | 7.8 |
| 7.0 | 154 | 8.6 |
| 7.5 | 169 | 9.4 |
| 8.0 | 183 | 10.1 |
| 9.0 | 212 | 11.8 |
| 10.0 | 240 | 13.3 |
| 11.0 | 269 | 14.9 |
| 12.0 | 298 | 16.5 |
FAQ
Should I use fasting glucose or all readings for the average?
Use all readings — fasting, pre-meal, post-meal, and bedtime. A1C reflects 24-hour average exposure to glucose, so using only fasting values will underestimate it, and using only post-meal values will overestimate it.
Why doesn’t my estimated A1C match my lab A1C?
The equation assumes a typical red blood cell lifespan (~120 days) and normal hemoglobin. Conditions like iron deficiency, hemolytic anemia, chronic kidney disease, recent blood loss, or hemoglobin variants (e.g., sickle cell trait) can push your lab A1C higher or lower than the estimate. A CGM-derived average over 14+ days usually tracks closer to lab A1C than a small number of fingerstick readings.
What units should I enter?
Either mg/dL (common in the US) or mmol/L (common in the UK, Canada, Australia, and most of Europe). The calculator converts automatically — just pick the unit that matches your meter.
How many readings do I need for a reliable estimate?
At least 10–14 days of readings spread across the day is a reasonable minimum. A handful of readings from one time of day will bias the result and shouldn’t be used to predict your next lab A1C.
