HbA1c calculator — glycated haemoglobin and average glucose
Convert HbA1c between % and mmol/mol and to estimated average glucose (ADAG formula), or the other way round, and compare it with diagnostic criteria and treatment targets.
Interpretation
HbA1c reflects average glucose over the previous 2–3 months (the red cell lifespan). In people without known diabetes:
- below 5.7% (39 mmol/mol) — normal,
- 5.7–6.4% (39–47 mmol/mol) — may indicate prediabetes; check fasting glucose or an OGTT,
- 6.5% (48 mmol/mol) or more — a diagnostic criterion for diabetes (standardised assay, usually confirmed by a second test).
Treatment targets
- ≤ 7.0% (53 mmol/mol) — general target in diabetes,
- ≤ 6.5% (48 mmol/mol) — type 1 diabetes, type 2 diabetes of short duration (< 5 years), children and adolescents, if this does not increase the risk of hypoglycaemia,
- 8.0–8.5% (64–69 mmol/mol) — older people with long-standing diabetes, macrovascular complications or multiple comorbidities and a life expectancy under 10 years,
- < 6.5% (48 mmol/mol) in women with diabetes planning pregnancy and < 6.0% (42 mmol/mol) in the second and third trimester, if this does not increase hypoglycaemia.
How we calculate
Estimated average glucose (eAG) from the ADAG study:
eAG [mg/dl] = 28,7 × HbA1c [%] − 46,7
HbA1c unit conversion (IFCC–NGSP master equation):
IFCC [mmol/mol] = (NGSP [%] − 2,15) × 10,929
Glucose in mmol/L = mg/dL ÷ 18.016.
| HbA1c [%] | HbA1c [mmol/mol] | eAG [mg/dl] | eAG [mmol/l] |
|---|---|---|---|
| 5.0 | 31 | 97 | 5.4 |
| 6.0 | 42 | 126 | 7.0 |
| 6.5 | 48 | 140 | 7.8 |
| 7.0 | 53 | 154 | 8.6 |
| 8.0 | 64 | 183 | 10.2 |
| 9.0 | 75 | 212 | 11.7 |
| 10.0 | 86 | 240 | 13.3 |
| 11.0 | 97 | 269 | 14.9 |
| 12.0 | 108 | 298 | 16.5 |
Limitations
- HbA1c can be falsely low when red cell survival is shortened (haemolysis, bleeding, pregnancy, erythropoietin) and falsely high in iron deficiency.
- Haemoglobin variants and chronic kidney disease can distort the result depending on the assay.
- eAG is an estimate; the same HbA1c can match different average glucose in different people. For CGM users, time in range (TIR) matters more.
Sources
- Polskie Towarzystwo Diabetologiczne. Zalecenia kliniczne dotyczące postępowania u osób z cukrzycą — 2026. Current Topics in Diabetes, rozdział 4. ptdiab.pl
- Nathan DM, Kuenen J, Borg R, et al. Translating the A1C assay into estimated average glucose values (ADAG). Diabetes Care 2008;31:1473–1478. doi.org
- Hoelzel W, Weykamp C, Jeppsson JO, et al. IFCC reference system for measurement of hemoglobin A1c in human blood and the national standardization schemes. Clin Chem 2004;50:166–174. doi.org
Frequently asked questions
What is an HbA1c of 7% in mmol/mol?
An HbA1c of 7.0% equals 53 mmol/mol and corresponds to an average glucose of about 154 mg/dL (8.6 mmol/L).
Which HbA1c means diabetes?
An HbA1c of 6.5% (48 mmol/mol) or more, measured with a standardised assay, is a diagnostic criterion for diabetes. 5.7–6.4% may indicate prediabetes.
How often should HbA1c be checked?
In people with diabetes usually every 3–6 months, more often after a change in treatment or when the target is not met.
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This calculator is for education and does not replace a doctor’s assessment. Always interpret the result together with the history and examination.