HbA1c to Average Glucose (eAG) Calculator
Convert HbA1c into estimated average glucose, and switch between DCCT (%) and IFCC (mmol/mol) units and mg/dL or mmol/L.
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Equivalent HbA1c in the other unit: —
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What Estimated Average Glucose Means
HbA1c reflects glucose exposure over the previous two to three months, weighted towards the most recent weeks. The estimated average glucose (eAG) expresses that same information in the units people see on a meter, which makes the number far easier to act on. The relationship was established by the ADAG study, which compared continuous glucose monitoring averages with HbA1c in more than 500 people and produced a linear equation that is now used by laboratories and diabetes organisations worldwide.
The Conversion Formulas
- DCCT % to eAG (mg/dL): eAG = 28.7 × HbA1c − 46.7
- DCCT % to eAG (mmol/L): eAG = 1.59 × HbA1c − 2.59
- IFCC to DCCT: DCCT % = (IFCC mmol/mol × 0.09148) + 2.152
- eAG back to HbA1c: HbA1c = (eAG mg/dL + 46.7) ÷ 28.7
A worked example: HbA1c of 7.0 % gives eAG = 28.7 × 7.0 − 46.7 = 154 mg/dL, and 1.59 × 7.0 − 2.59 = 8.5 mmol/L from the published SI equation. Published conversion tables usually round the same point to 8.6 mmol/L, because they convert the mg/dL figure directly; the difference is rounding, not disagreement. HbA1c of 7.0 % is 53 mmol/mol in IFCC units.
DCCT and IFCC: Two Ways to Report the Same Test
There are two standardised ways to report HbA1c, and they are not interchangeable numbers. The DCCT/NGSP system reports a percentage, the familiar 7 %; the IFCC system reports mmol/mol of haemoglobin, where 7 % is 53 mmol/mol. Most laboratories report both, but a value read in the wrong unit — 53 versus 5.3 — leads to a very different-looking estimate, which is why this calculator asks which unit you are using.
When the Estimate Is Least Reliable
- Anaemia and blood loss — iron deficiency, chronic disease and recent transfusion all change red-cell survival
- Haemoglobin variants — sickle cell trait, thalassaemia and HbE can distort results depending on the assay
- Chronic kidney disease and erythropoietin therapy — shortened red-cell survival lowers HbA1c independently of glucose
- Pregnancy — haemodilution and accelerated red-cell turnover mean HbA1c under-represents recent glucose
- Very recent changes — a new treatment takes two to three months to be fully reflected
For anyone using continuous glucose monitoring, the Glucose Management Indicator (GMI) is a better-matched statistic: GMI (%) = 3.31 + 0.02392 × mean glucose in mg/dL. It answers the same question as eAG but is derived from the same sensor data rather than converted from HbA1c.
Frequently Asked Questions
Is eAG the same as my meter average?
No. From the same average glucose, HbA1c-derived eAG and a meter average usually differ by a small amount because meters, test timing and red-cell lifespan all vary. Treat eAG as a translation, not a measurement.
What is 53 mmol/mol in percent?
53 mmol/mol is 7.0 %. The conversion is DCCT % = (IFCC × 0.09148) + 2.152.
Can I use eAG to set my insulin doses?
No. Insulin adjustment is based on current glucose patterns, meals and activity, with clinical supervision. eAG describes an average over months and hides exactly the variation that matters for dosing.