HbA1c to Average Glucose Calculator (eAG)
Turn an HbA1c result into the average glucose it reflects — and back.
Where it sits on the ADA 2026 HbA1c ranges
- Normal: below 5.7% (39 mmol/mol)
- Prediabetes: 5.7–6.4% (39–47)
- Diabetes: 6.5% (48) or more
HbA1c and average glucose in the ADAG study
The middle column is the eAG; the range in brackets is the 95% prediction interval — where most people with that HbA1c actually were (Nathan et al., Table 2).
| HbA1c | IFCC | eAG mg/dL (95% range) | eAG mmol/L (95% range) |
|---|
Before relying on an HbA1c
The ADA (Standards of Care 2026, Table 2.3) lists these as reasons an HbA1c may not match real glucose levels:
- Red-cell turnover: anaemia, iron deficiency or other changes in iron status, recent blood loss or transfusion, haemolysis, splenectomy, erythropoietin treatment.
- Conditions: pregnancy, kidney failure or dialysis, liver cirrhosis, HIV (may read low), G6PD deficiency (the G202A variant lowers it by about 0.7–0.8%).
- Lab method: haemoglobin variants such as sickle cell trait, severe hypertriglyceridaemia or hyperbilirubinaemia can interfere with some assays.
In these cases the ADA recommends glucose tests for diagnosis. Tell your doctor if your HbA1c and your meter or CGM disagree.
For general information only, not medical advice. Consult a qualified health professional for advice about your situation.
About the HbA1c to Average Glucose Calculator (eAG)
HbA1c (glycated haemoglobin, also written A1C) shows how much glucose has stuck to your red blood cells over roughly the last three months. Labs report it in two units: % (NGSP/DCCT, used for example in the US and India) or mmol/mol (IFCC, used for example in the UK and much of Europe). This calculator converts between them and turns the result into the estimated average glucose (eAG) it corresponds to, in mg/dL and mmol/L — the same units as a glucose meter.
It uses the ADAG study equation adopted by the American Diabetes Association (ADA), shows which ADA 2026 range a laboratory HbA1c falls in (normal, prediabetes or diabetes), and lists the conditions that can make HbA1c misleading. It also works the other way: enter an average glucose, or the mean glucose from a continuous glucose monitor (CGM) to get its glucose management indicator (GMI). Nothing you enter leaves your browser.
How to use it
- Choose what you have: an HbA1c result, an average glucose (for example from your meter’s 90-day average) or a CGM mean glucose.
- Type the number and pick its unit — % or mmol/mol for HbA1c, mg/dL or mmol/L for glucose. The calculator warns you if the number looks like it is in the other unit.
- Read the estimated average glucose (or HbA1c), the conversion to the other unit and, for a lab HbA1c, the ADA category. The ADAG table below shows the range of averages that people with the same HbA1c actually had.
- Copy the result, or check the list of conditions that make HbA1c less reliable before drawing conclusions.
Examples
53 mmol/mol · eAG 28.7 × 7.0 − 46.7 = 154 mg/dL (8.6 mmol/L) · ADA diabetes range
0.09148 × 42 + 2.152 = 6.0% · eAG 125 mg/dL (7.0 mmol/L) · prediabetes range (39–47 mmol/mol)
36 mmol/mol · eAG 108 mg/dL (6.0 mmol/L) · normal range (below 5.7%)
GMI 3.31 + 0.02392 × 150 = 6.9% (52 mmol/mol)
The formulas
- eAG (ADAG study): eAG (mg/dL) = 28.7 × A1C (%) − 46.7, and eAG (mmol/L) = 1.5944 × A1C − 2.594. The study measured about 2,700 glucose readings over three months in each of 507 adults (268 with type 1 diabetes, 159 with type 2 and 80 without diabetes) and found a linear relationship with R² = 0.84.
- % ↔ mmol/mol (NGSP master equation): NGSP (%) = 0.09148 × IFCC (mmol/mol) + 2.152, so IFCC = (NGSP − 2.152) ÷ 0.09148. Each 1% step is about 11 mmol/mol.
- GMI from a CGM: GMI (%) = 3.31 + 0.02392 × mean glucose (mg/dL), or GMI (mmol/mol) = 12.71 + 4.70587 × mean glucose (mmol/L). The ADA describes GMI as a calculated value approximating A1C — not always equivalent to it.
- Glucose units: 1 mmol/L = 18.0156 mg/dL (glucose is 180.156 g/mol).
- Average glucose → HbA1c: the calculator solves the ADAG mg/dL equation backwards. That shows the HbA1c the ADAG line links to your average; it is not a measurement.
What the HbA1c ranges mean (ADA 2026)
- Normal: below 5.7% (below 39 mmol/mol).
- Prediabetes: 5.7–6.4% (39–47 mmol/mol). The ADA notes that risk is continuous and starts below this range.
- Diabetes: 6.5% or more (48 mmol/mol or more), measured by an NGSP-certified, DCCT-standardised lab method. Without unequivocal high blood sugar, a diagnosis needs two abnormal results — for example HbA1c repeated, or HbA1c with a fasting glucose.
- Goal for many adults who have diabetes: below 7% (53 mmol/mol), if this can be reached without significant hypoglycaemia; your care team may set a different goal.
The categories apply to a laboratory HbA1c. They do not apply to an eAG, a GMI or an HbA1c estimated from an average glucose.
When HbA1c can be misleading
HbA1c depends on how long red blood cells live, so anything that changes red-cell turnover changes the result without any change in glucose. The ADA (2026, Table 2.3) lists:
- Anaemia, iron deficiency or other changes in iron status, blood loss, transfusion, haemolysis, splenectomy and erythropoietin treatment
- Pregnancy, kidney failure and dialysis, liver cirrhosis, HIV (HbA1c may underestimate glucose) and G6PD deficiency (the common G202A variant lowers HbA1c by about 0.7–0.8%)
- Haemoglobin variants such as sickle cell trait, and severe hypertriglyceridaemia or hyperbilirubinaemia, which interfere with some lab methods — a method free of interference should be used
In these situations the ADA recommends plasma glucose tests for diagnosis. The ADAG study enrolled adults aged 18–70 with stable glucose and excluded children, pregnant women and people with anaemia, haemoglobinopathies, kidney or liver disease. If your HbA1c and your glucose readings disagree, tell your doctor.
Sources
- Nathan DM, Kuenen J, Borg R, et al. Translating the A1C assay into estimated average glucose values. Diabetes Care 31(8):1473-8 (Table 2 and its footnote)
- American Diabetes Association. 2. Diagnosis and Classification of Diabetes: Standards of Care in Diabetes—2026. Diabetes Care 49(Suppl 1):S27-S49 (Tables 2.1–2.3)
- American Diabetes Association. 6. Glycemic Goals, Hypoglycemia, and Hyperglycemic Crises: Standards of Care in Diabetes—2026. Diabetes Care 49(Suppl 1):S132-S149 (Tables 6.1–6.3)
- NGSP. IFCC standardization of HbA1c (master equation) and conversion table; Hoelzel W et al. Clin Chem 50:166-74
- Bergenstal RM, Beck RW, Close KL, et al. Glucose Management Indicator (GMI). Diabetes Care 41(11):2275-80
Limitations
- An eAG is the average that matches your HbA1c on the ADAG line. Real averages vary: at 7% the middle 95% of people in the study averaged 123–185 mg/dL.
- 98.5% of the ADAG samples had an HbA1c between 4% and 10%; above that, and especially above 12%, the estimate rests on few measurements.
- An IFCC value below 20 mmol/mol (under 4%) is almost always a percentage entered with the wrong unit, so the calculator asks you to check it.
- GMI needs a CGM mean from at least 10–14 days of data. In the GMI paper it differed from the lab HbA1c by 0.5 percentage points or more 28% of the time, and it was derived with one brand of sensor.
- Accepted ranges: HbA1c 3–20% (9–195 mmol/mol), glucose 40–600 mg/dL (2.2–33.3 mmol/L).
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Frequently asked questions
What average blood sugar does an HbA1c of 7% mean?
About 154 mg/dL (8.6 mmol/L), using the ADAG equation 28.7 × 7 − 46.7. In the study, people with an HbA1c of 7% had averages from about 123 to 185 mg/dL, so your own average may differ.
How do I convert HbA1c from mmol/mol to %?
Multiply by 0.09148 and add 2.152 — for example 48 mmol/mol × 0.09148 + 2.152 = 6.5%. To go from % to mmol/mol, subtract 2.152 and divide by 0.09148.
What HbA1c is prediabetes?
The ADA defines prediabetes as an HbA1c of 5.7–6.4% (39–47 mmol/mol). 6.5% (48 mmol/mol) or more is in the diabetes range, which needs a second abnormal test to confirm unless glucose is unmistakably high.
Why does my HbA1c not match my meter readings?
Finger-stick readings are snapshots and may miss highs after meals or lows at night. HbA1c can also be thrown off by anaemia, recent blood loss or transfusion, pregnancy, kidney disease and some haemoglobin variants. Ask your doctor; tests such as fructosamine or a CGM can help.
What is GMI and is it the same as HbA1c?
GMI (glucose management indicator) is an HbA1c-like number calculated from the mean glucose of a continuous glucose monitor. It is an estimate, not a blood test, and the two often differ — use both with your care team.