Convert HbA1c to estimated average glucose (eAG), or view the algebraic HbA1c equivalent of an eAG value. eAG is not a spot glucose reading or a CGM average.
Values are calculated on this page only; they are not sent to or saved on a server.
What do HbA1c and eAG measure?
HbA1c, also called A1C, measures how much hemoglobin has glucose attached to it and reflects glucose exposure over roughly the preceding two to three months. Estimated average glucose (eAG) translates that result into familiar glucose units using a statistical relationship. It is not a new fasting or after-meal glucose measurement.
For example, an A1C of 7% gives an eAG of 154.2 mg/dL. This does not mean glucose stayed at 154.2 all day. The same average can coexist with different highs, lows, and glucose patterns, so finger-stick records or continuous glucose monitoring (CGM) data provide additional information.
Choose the conversion direction and input unit
- Select Conversion direction: HbA1c → eAG or eAG → HbA1c equivalent.
- Enter one Input value and select the matching Input unit. For HbA1c, choose % (NGSP) or mmol/mol (IFCC). For eAG, choose mg/dL or mmol/L.
- The lab date is optional. If provided, enter a complete, valid date no later than today, then select Calculate and explain.
HbA1c in mmol/mol and glucose in mmol/L are different units. Check the unit on the laboratory report. An IFCC input is converted to NGSP % before calculating eAG. Reverse mode gives an algebraic equivalent, not a measured laboratory A1C or a validated individual prediction. The NGSP conversion tool also distinguishes these units.
This tool accepts HbA1c 3–20% or the corresponding IFCC range, and eAG 39.4–527.3 mg/dL or that range divided by 18 in mmol/L. The exact mmol/L boundaries are 39.4 / 18 and 527.3 / 18, approximately 2.188889–29.294444. These are software input limits intended to catch errors, not a statement that individual predictions are validated throughout the range. Very high or low laboratory results need clinical interpretation.
Formula and worked examples
The ADAG study derived eAG (mg/dL) = 28.7 × A1C (%) − 46.7. This calculator also divides the result by 18 to show an approximate mmol/L equivalent. Reverse mode uses [eAG in mg/dL + 46.7] / 28.7 to find a corresponding point on that line. An eAG input in mmol/L is first multiplied by 18. Intermediate values are not rounded; eAG and HbA1c % are displayed to one decimal place, and IFCC mmol/mol to the nearest integer.
| A1C | eAG mg/dL | eAG mmol/L |
|---|---|---|
| 5.0% | 96.8 | 5.4 |
| 6.0% | 125.5 | 7.0 |
| 7.0% | 154.2 | 8.6 |
| 8.0% | 182.9 | 10.2 |
At 7%, the arithmetic is 28.7 × 7 − 46.7 = 154.2. Entering 154.2 in reverse mode returns 7%. Display values are rounded to one decimal place. These examples are not a table of recommended treatment targets.
Can the reverse result predict my A1C?
Rearranging the equation does not make it a validated prediction of an individual's laboratory A1C. The original study described a population relationship, and individuals can differ from that relationship. Do not enter one fasting glucose measurement, such as 154 mg/dL, and interpret the output as your A1C.
CGM reports may include a glucose management indicator (GMI), which is a separate metric. The reverse equivalent here, GMI, and measured A1C should not be treated as interchangeable test results.
When A1C and glucose records disagree
Some anemias, recent bleeding or transfusion, altered red-cell lifespan, hemoglobin variants, pregnancy, and dialysis can affect A1C interpretation. A repeated discrepancy deserves a review of the clinical context, timing, and laboratory method rather than an assumption that one number is automatically wrong.
Diagnostic thresholds and personal treatment goals are separate questions. This calculator does not diagnose diabetes, adjust medication, or detect hypoglycemia. The fasting glucose and A1C guide explains testing conditions and the role of confirmation.
Frequently asked questions
Should fasting glucose and eAG be the same?
No. Fasting glucose is a measurement at a particular time; eAG is an A1C-derived average equivalent. They describe different aspects of glycemia.
If the calculated value falls, can I reduce my medication?
A conversion alone is not enough to change treatment. Review laboratory trends, low-glucose episodes, medicines, and your individual targets with your clinical team.
Questions to bring to an appointment
- Could anemia, a recent transfusion, kidney disease, or another factor affect my A1C?
- Does the difference from my glucose meter or CGM records need investigation?
- What testing interval and treatment goal apply to me?
Related tools and sources
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- Nathan et al., ADAG study (2008): eAG equation
- ADAG erratum (2009): corrected coefficients for the mmol/L table · NGSP: HbA1c and eAG reference table
- NIDDK: A1C testing and limitations
- NGSP: IFCC standardization and units
- Diabetes Care (2024): GMI and measured A1C
Prepared and sources checked by Life Choice Note, 26 September 2026. This is general education checked against the cited sources, not independently physician-reviewed guidance or an individual diagnosis, treatment, or exercise prescription. Editorial standards · Terms and disclaimer