Estimate A1C from average glucose, reverse an A1C to eAG, or summarize multiple glucose readings using the published ADAG regression.
Related Calculators
Formula
The calculator uses the ADAG (A1C-Derived Average Glucose) equation from Nathan et al., 2008, as documented by NGSP. Inverting the regression gives an algebraic A1C-equivalent estimate, not a separately validated individual prediction. It is not the distinct CGM-derived GMI equation.
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
Laboratory A1C reflects glucose exposure over preceding months. The following categories apply to appropriately performed laboratory A1C testing, not to this calculator’s inferred percentage or to a short reading list. Diagnosis and individualized targets require clinical assessment; see NIDDK’s A1C guidance.
- 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% — An illustrative treatment target used for many adults with diabetes; individual targets differ (eAG ~154 mg/dL)
The eAG is a statistical estimate, not a lab measurement. Your actual A1C from a blood draw can differ materially 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 | 10.2 |
| 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 representative sampling across the relevant period. Selecting only particular times can bias the average; no direction or size of error is guaranteed for an individual. This tool equally weights submitted readings. Its range fraction is a percentage of those readings, not CGM time-in-range.
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. Neither a short glucose list nor the inverse ADAG equation replaces laboratory testing. Discuss substantial differences with your clinician.
What units should I enter?
Choose mg/dL or mmol/L to match the entered glucose values. Changing the glucose-unit selection reinterprets the existing numbers rather than converting them. In the reverse mode, the selection determines the eAG output unit.
How many readings do I need for a reliable estimate?
There is no universal minimum count or duration that makes an arbitrary reading list a reliable laboratory-A1C prediction. Sampling coverage, timing, measurement quality and individual biology matter. Use the list mode for descriptive statistics of the submitted set; do not diagnose diabetes or change medication from its estimated percentage.
