A1C & Estimated Average Glucose (eAG) Calculator
Convert between A1C and estimated average glucose (eAG) with the ADAG relationship.
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How this calculator works
The ADAG relationship is eAG (mg/dL) = 28.7 × A1C (%) − 46.7. The reverse conversion rearranges that relationship. Glucose in mmol/L is converted using 18 mg/dL per mmol/L.
An estimated A1C does not replace a laboratory measurement and is not the CGM-specific GMI equation. Red-cell turnover, some hemoglobin variants and other clinical factors can affect A1C. This tool does not diagnose diabetes or suggest medication doses.
Method implementation checked October 28, 2026. Educational information, not a diagnosis or a treatment recommendation.
A1C and estimated average glucose: two ways to read blood sugar
A1C reports the percentage of hemoglobin with glucose attached. Estimated average glucose, or eAG, expresses that result in the glucose units used by meters. The conversion helps you understand the scale of a laboratory result, but an average cannot show when glucose rose, how low it fell or how much it varied during a day. [1]
What does an A1C-to-eAG conversion look like?
Using the ADAG relationship, an A1C of 7% corresponds to an eAG of about 154 mg/dL, or 8.6 mmol/L. That does not mean every reading was 154. Two people can have the same average with different patterns of highs and lows. This is a conversion example, not a personal glucose target. [1]
- A1C is a percentage, not a glucose concentration.
- eAG uses mg/dL or mmol/L, just like glucose measurements.
- A change in units changes the number displayed, not the underlying glucose estimate.
Why can’t a fasting glucose result substitute for an average?
One fasting result describes one point in time. A1C reflects glucose exposure over roughly three months. Entering a single fasting or post-meal reading into the reverse conversion can produce a number, but it cannot reconstruct the months of glucose exposure represented by a laboratory A1C. [2]
Why might a lab A1C disagree with glucose readings?
The relationship is not identical for every person. Conditions that alter red blood cell lifespan, some hemoglobin variants and differences in the time periods covered can affect the comparison. Before assuming either number is wrong, check what was measured and when. [2]
- Match the dates covered by your glucose average with the laboratory draw.
- Distinguish a measured A1C from one calculated from glucose.
- Keep any relevant blood-count or hemoglobin information with the report.
Is this the same estimate a CGM app shows?
A continuous glucose monitor may report glucose management indicator, or GMI. GMI uses a different equation from this ADAG conversion, so the two estimates need not match even when calculated from the same average glucose. Keep the method label with the number when tracking A1C changes and follow-up results. [3]
Build a blood-sugar baseline you can follow
Read the guide to A1C changes and follow-up testing- If you started with glucose readings, a laboratory HbA1c gives you a measured A1C to compare with the estimate. If you already have a lab result, it becomes a baseline for follow-up.
- Fasting glucose shows your blood sugar at the time of the draw. Adding fasting insulin helps put that value in the context of how much insulin your body is producing.
- With Mito membership, your clinician-reviewed results become an action plan. Follow-up HbA1c testing helps you track average blood sugar as you put that plan into practice.
References
Frequently asked questions
Does the conversion diagnose prediabetes or diabetes?
No. An A1C estimated from average glucose is not a diagnostic laboratory result. Do not apply diagnostic A1C thresholds to this estimate as though it were a measured test. [2]
Can I enter A1C in mmol/mol?
This calculator accepts A1C as a percentage. The mmol/L option is for average glucose, not A1C in mmol/mol. Check the measurement label as well as the number before converting.
Do I need to fast for an A1C test?
An A1C test by itself does not require fasting. Other tests ordered with it may have different preparation requirements, so follow the instructions for your full order. [2]
Can two people with the same A1C have different glucose patterns?
Yes. An average can conceal different highs and lows. A1C and eAG do not show glucose variability or the timing of changes during the day. [2]
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