Convert A1C to average glucose and back
This A1C calculator turns a haemoglobin A1C (HbA1c) result into the estimated average glucose (eAG) it corresponds to, in mg/dL and mmol/L, and converts between the two A1C units: percent (NGSP, used in the US and India) and mmol/mol (IFCC, used in the UK, Europe and Australia). Type in any of the four boxes and the rest follow.
It uses the same ADAG equation the American Diabetes Association uses for its eAG figures, shows the working, marks where the value sits against the ADA diagnostic ranges, and includes an A1C chart from 4% to 14%.
It is information only and not a diagnosis; ask your doctor what your own result means.
How to use the A1C calculator
- Type your HbA1c in % or mmol/mol from your lab report.
- Read the estimated average glucose in mg/dL and mmol/L, and the other A1C unit.
- To go the other way, type an average glucose (for example from a meter or sensor report) and read the matching A1C.
- Use the A1C chart below the result for common values; tap a row to load it.
A1C Calculator features
Four-way conversion
A1C % ↔ mmol/mol ↔ eAG mg/dL ↔ eAG mmol/L, live in every direction.
ADA formula
The ADAG equation behind the ADA’s own eAG figures, with the arithmetic shown.
Diagnostic ranges
A colour scale and plain-language note against the ADA 2026 ranges.
Chart
Twenty-one rows from 4% to 14% in half-steps.
The formulas
The A1C-Derived Average Glucose study (Nathan DM et al., Diabetes Care 2008;31:1473–1478) measured about 2,700 glucose readings per person over three months in 507 adults with and without diabetes, and found eAG (mg/dL) = 28.7 × A1C − 46.7. For mmol/L the calculator divides by 18, as the ADA table does (the paper’s own form, 1.59 × A1C − 2.59, agrees to within 0.06 mmol/L).
Between the A1C units it uses the NGSP–IFCC master equation published by the NGSP: A1C % = 0.09148 × mmol/mol + 2.152, so mmol/mol = (% − 2.152) ÷ 0.09148. Example: 7% → 28.7 × 7 − 46.7 = 154 mg/dL = 8.6 mmol/L, and (7 − 2.152) ÷ 0.09148 = 53 mmol/mol. Checked 24 October 2026.
ADA table: A1C and eAG with 95% confidence intervals
The range in brackets shows how far the true average glucose of most people with that A1C can sit from the estimate. Source: American Diabetes Association, Standards of Care in Diabetes—2024, Table 6.1, adapted from Nathan et al.
| A1C | eAG mg/dL (95% CI) | eAG mmol/L (95% CI) |
|---|---|---|
| 5% | 97 (76–120) | 5.4 (4.2–6.7) |
| 6% | 126 (100–152) | 7.0 (5.5–8.5) |
| 7% | 154 (123–185) | 8.6 (6.8–10.3) |
| 8% | 183 (147–217) | 10.2 (8.1–12.1) |
| 9% | 212 (170–249) | 11.8 (9.4–13.9) |
| 10% | 240 (193–282) | 13.4 (10.7–15.7) |
| 11% | 269 (217–314) | 14.9 (12.0–17.5) |
| 12% | 298 (240–347) | 16.5 (13.3–19.3) |
What the ranges mean, and the limits
- For non-pregnant people the ADA Standards of Care in Diabetes—2026 use an A1C of 6.5% (48 mmol/mol) or higher for diabetes and 5.7–6.4% (39–47 mmol/mol) for prediabetes, normally confirmed by a repeat test. Targets for people with diabetes are set individually with their care team.
- A1C reflects roughly the last two to three months. Anything that changes red blood cell lifespan — anaemia, blood loss, kidney disease, pregnancy, some haemoglobin variants — can make it misleading.
- eAG is not the same as a fasting reading or a meter average; meter averages lean towards the times you test. To track readings, use the blood sugar log; for single readings, the mg/dL to mmol/L converter.
A1C Calculator FAQ
How do I convert A1C to average blood sugar?
Multiply the A1C by 28.7 and subtract 46.7 to get mg/dL; divide by 18 for mmol/L. An A1C of 6% is about 126 mg/dL (7.0 mmol/L). The A1C calculator above does it for you.
What is 48 mmol/mol as a percentage?
0.09148 × 48 + 2.152 = 6.5%, the ADA threshold for diabetes.
Is this the ADA A1C calculator formula?
Yes — the ADA’s eAG figures come from the same ADAG equation, so the results match its table.
Why does my meter average differ from my eAG?
Meters only see the moments you test, often before meals, while A1C reflects the whole day and night over months. Individual differences in red blood cells also matter.
Can I use this A1C calculator online to diagnose diabetes?
No. It converts numbers for information. Diagnosis needs laboratory tests, usually repeated, interpreted by a doctor.
What is a normal A1C?
Below 5.7% (39 mmol/mol) is below the ADA prediabetes range for non-pregnant adults. Your doctor will interpret your result with your history.