A1C Calculator – HbA1c to Average Blood Sugar (eAG)
Convert HbA1c between percent (DCCT) and mmol/mol (IFCC) units, and see the estimated average glucose (eAG) it represents. Enter your lab result and choose its unit.
Convert HbA1c Between % and mmol/mol
HbA1c Formula
Where:
- \(\text{HbA1c (\%)}\) — glycated hemoglobin in DCCT percentage units
- \(\text{HbA1c (mmol/mol)}\) — glycated hemoglobin in IFCC units
- \(\text{eAG}\) — estimated average glucose over the previous 2–3 months
The first two equations are the IFCC/DCCT "master equation" used to translate between the two reporting systems. The eAG equations come from the ADAG study and estimate the average blood glucose that corresponds to a given HbA1c.
HbA1c – Calculation Example
Example: a lab report shows an HbA1c of 7.5%, and you want the IFCC value and the corresponding average glucose.
\[
\text{mmol/mol} = (7.5 - 2.15) \times 10.929 = 5.35 \times 10.929 \approx 58
\]
\[
\text{eAG} = 28.7 \times 7.5 - 46.7 = 215.25 - 46.7 \approx 169 \text{ mg/dL}
\]
\[
\text{eAG} = \frac{168.55}{18} \approx 9.4 \text{ mmol/L}
\]
Result: an HbA1c of 7.5% equals 58 mmol/mol, corresponding to an estimated average glucose of about 169 mg/dL (9.4 mmol/L).
How to Use the HbA1c Calculator
- Enter your lab result in the HbA1c value field.
- Select the unit your lab used — % (DCCT, common in the US) or mmol/mol (IFCC, used in Europe, the UK, Canada, Australia and many other countries) — in the Unit dropdown next to the value.
- Read your HbA1c expressed in both unit systems, plus the estimated average glucose in mg/dL and mmol/L.
- Check the What this means section for the general interpretation of your result.
What Is HbA1c and Why Are There Two Units?
HbA1c, or glycated hemoglobin, measures the percentage of hemoglobin in your red blood cells that has glucose attached to it. Because red blood cells live for roughly three months, HbA1c reflects your average blood sugar over the past 2–3 months — it is not affected by a single meal or a fast on the day of the test. This makes it the standard test for monitoring diabetes and one of the main tests for diagnosing it.
Two reporting systems coexist. The United States reports HbA1c as a percentage (DCCT units), for example 7.5%. Most of the rest of the world reports it in mmol/mol (IFCC units), for example 58 mmol/mol, which is a true concentration unit. The two scales are related by the IFCC/DCCT master equation shown above, so any value can be converted exactly in either direction — 6.5% is exactly 48 mmol/mol.
Alongside the conversion, the calculator shows the estimated average glucose (eAG). This translates your HbA1c into the everyday glucose numbers a meter would show, which many people find easier to relate to: an HbA1c of 7% corresponds to an eAG of about 154 mg/dL (8.6 mmol/L). Keep in mind that eAG is a statistical estimate derived from the ADAG study, not a measurement of your personal glucose — individuals can differ from the average.
Interpreting the Result
According to the American Diabetes Association diagnostic criteria for adults without diabetes:
- Below 5.7% (below 39 mmol/mol) — normal range.
- 5.7–6.4% (39–46 mmol/mol) — prediabetes range; lifestyle changes can reduce the risk of progressing to type 2 diabetes.
- 6.5% (48 mmol/mol) or higher — diabetes range (a diagnosis always requires confirmation by a health professional).
For people who already have diabetes, targets are individual. The ADA often suggests aiming for below 7% (53 mmol/mol), but your doctor may recommend a tighter or looser target depending on your age, treatment, hypoglycemia risk and other conditions.
Assumptions and Limitations
- The % ↔ mmol/mol conversion is exact per the IFCC/DCCT master equation; the eAG is an estimate and can deviate from your true average by a meaningful margin.
- Conditions that change red blood cell turnover — anemia, recent blood loss or transfusion, pregnancy, hemoglobin variants, kidney disease — can make HbA1c inaccurate regardless of units.
- The interpretation thresholds apply to adults without diabetes; diagnostic thresholds differ for children and during pregnancy.
- This calculator is for information only and does not replace medical advice or a diagnosis from your healthcare provider.
Quick Reference Table
| HbA1c (%) | HbA1c (mmol/mol) | eAG (mg/dL) | eAG (mmol/L) |
|---|---|---|---|
| 5.0 | 31 | 97 | 5.4 |
| 5.7 | 39 | 117 | 6.5 |
| 6.0 | 42 | 126 | 7.0 |
| 6.5 | 48 | 140 | 7.8 |
| 7.0 | 53 | 154 | 8.6 |
| 7.5 | 58 | 169 | 9.4 |
| 8.0 | 64 | 183 | 10.2 |
| 9.0 | 75 | 212 | 11.8 |
| 10.0 | 86 | 240 | 13.3 |
If you also work with day-to-day glucose readings, try our blood sugar converter for mg/dL and mmol/L values, or the cholesterol unit converter for lipid panels, which are often reported in different units around the world.
Frequently Asked Questions
How do I convert HbA1c from mmol/mol to percent by hand?
Divide the IFCC value by 10.929 and add 2.15: \( \text{HbA1c (\%)} = \frac{\text{mmol/mol}}{10.929} + 2.15 \). For example, 58 mmol/mol gives \( 58 \div 10.929 + 2.15 \approx 7.5\% \). To go the other way, subtract 2.15 from the percentage and multiply by 10.929. This is the official IFCC/DCCT master equation, so the result is exact.
Why does the US use % and other countries use mmol/mol?
The % unit (DCCT) comes from the historic American DCCT trial and reflects the proportion of glycated hemoglobin relative to total hemoglobin. In 2010 many countries adopted the IFCC standard, which reports a true concentration of glycated hemoglobin in mmol/mol. Both describe the same thing — labs simply report on different scales, which is why a converter is handy when reading foreign lab reports or research papers.
What is a good HbA1c target for someone with diabetes?
Many guidelines, including the ADA, suggest aiming for below 7% (53 mmol/mol), but targets are individual. Older adults, people with heart or kidney disease, or those at risk of severe hypoglycemia may be advised to stay below 7.5–8% instead, while younger, healthy patients may aim tighter, e.g. below 6.5%. Always discuss your personal target with your diabetes care team rather than adjusting treatment yourself.
Is eAG the same as my average meter readings?
Not necessarily. eAG is a statistical estimate from the ADAG study: some people's true average glucose runs higher or lower than the formula predicts, sometimes by 15–30 mg/dL or more. If your meter averages differ noticeably from your eAG, neither is wrong — the estimate is population-based. Conditions like anemia or hemoglobin variants can also distort HbA1c, making eAG unreliable for you personally.
Can HbA1c be wrong if I have anemia or another blood condition?
Yes. HbA1c assumes a normal red blood cell lifespan of about 120 days. Iron deficiency anemia, recent blood loss or transfusion, hemolytic anemia, pregnancy, kidney disease, and hemoglobin variants (like sickle cell trait) can all shift the result up or down regardless of your actual glucose. In these cases doctors may use alternatives such as fructosamine or continuous glucose monitoring instead.
What's the difference between HbA1c and fasting glucose or an OGTT?
HbA1c reflects average glucose over the past 2–3 months, while fasting glucose and the oral glucose tolerance test (OGTT) are snapshots at a single moment. They can disagree: someone with normal fasting glucose may still have a raised HbA1c, and vice versa. A diabetes diagnosis can be made by any of the three tests (HbA1c ≥ 6.5%, fasting glucose ≥ 126 mg/dL, or 2-hour OGTT ≥ 200 mg/dL), usually confirmed by a repeat test.
How do I convert eAG between mg/dL and mmol/L?
Divide mg/dL by 18 to get mmol/L, or multiply mmol/L by 18 to get mg/dL. For example, an eAG of 154 mg/dL equals about 8.6 mmol/L. The factor 18 works for all glucose conversions, not just eAG — the same math converts fingerstick meter readings between the US and metric systems.