A1C and Average Glucose Calculator
Convert average glucose to an ADAG-estimated A1C, or express an entered A1C as estimated average glucose (eAG). Supports mg/dL and mmol/L.
A calculated estimate is not a laboratory measurement or a diagnosis. Inputs stay in your browser.
Conversion result
Enter a value and calculate. Editing a value, unit or mode clears the previous result.
No diagnostic category is assigned to this estimate. Discuss laboratory results and treatment decisions with a clinician.
Formula and a worked example
The ADAG study by Nathan and colleagues related laboratory A1C to average glucose. This tool rearranges that published relationship:
Estimated A1C (%) = (average glucose in mg/dL + 46.7) ÷ 28.7
eAG (mg/dL) = 28.7 × A1C − 46.7
For 154 mg/dL, the estimate is (154 + 46.7) ÷ 28.7 = 6.993%, or about 7.0%. For an entered A1C of 7.0%, eAG is 154.2 mg/dL, about 8.56 mmol/L. Glucose conversion uses 18.018 mg/dL per mmol/L; rounding occurs only for display.
| A1C (%) | eAG (mg/dL) | eAG (mmol/L) |
|---|---|---|
| 5.0 | 97 | 5.4 |
| 5.7 | 117 | 6.5 |
| 6.0 | 125 | 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 | 11.7 |
| 10.0 | 240 | 13.3 |
How to interpret the estimate
Read the glucose report's dates and coverage. A fasting-only average omits other times of day. A short glucose report and a laboratory A1C, which reflects roughly three months with more influence from recent glucose, may describe different periods.
NGSP explains that shortened red-cell survival can lower A1C, while iron deficiency anemia is associated with higher A1C. Hemoglobin variants can affect results depending on the assay. The formula does not correct for these factors.
NIDDK's laboratory-testing guidance describes below 5.7%, 5.7–6.4%, and at least 6.5% as the normal, prediabetes, and diabetes thresholds for appropriate A1C testing. Diagnosis generally requires confirmation in the absence of clear symptoms. Those thresholds cannot diagnose a condition from this glucose-derived estimate.
GMI uses a different equation
The 2018 GMI study uses GMI (%) = 3.31 + 0.02392 × mean CGM glucose in mg/dL. At 183 mg/dL, GMI is 7.69% and the ADAG estimate is 8.00%. The difference follows from their fitted equations; it does not show which matches your laboratory A1C.
GMI is explained here for comparison; this editor provides the two ADAG/eAG conversion modes. A formula cannot convert GMI into your individual measured A1C.
Continue with the ADAG versus GMI comparison or the glucose conversion guide.
Questions about A1C conversion
How is A1C calculated?
A laboratory test measures glycated hemoglobin in blood. This calculator instead estimates A1C from average glucose using the ADAG relationship: estimated A1C (%) = (average glucose in mg/dL + 46.7) / 28.7. An average of 154 mg/dL gives about 7.0%. A calculated estimate cannot diagnose diabetes.
How to calculate A1C at home?
You can use a representative glucose average for an ADAG estimate. Check the dates and coverage of your CGM or meter report: a single reading or fasting-only average does not describe overall glucose exposure. The result is not a laboratory measurement and has no guaranteed margin of agreement with your lab A1C.
What is the formula for calculating A1C?
Estimated A1C (%) = (average glucose in mg/dL + 46.7) / 28.7. The reverse equation is eAG (mg/dL) = 28.7 × A1C - 46.7. This calculator multiplies mmol/L glucose by 18.018 before conversion and divides mg/dL by 18.018 for eAG in mmol/L.
Does this calculator compute GMI?
The tool provides average glucose to ADAG-estimated A1C and A1C to estimated average glucose (eAG). GMI uses a separate CGM-derived equation, explained below. It is not an additional calculator mode, and a formula cannot determine your individual laboratory A1C from GMI.
Why can estimated A1C differ from a lab result?
The glucose report and lab test may cover different periods. Glucose-data gaps, hemoglobin variants, red-cell conditions, and assay differences can affect the comparison. Hemolytic anemia can lower A1C, while iron deficiency anemia can raise it. Discuss persistent or unexpected differences with your clinician.