A1C to Estimated Average Glucose Calculator
Convert HbA1c percentage to estimated average glucose (eAG) in mg/dL or mmol/L using the ADA consensus formula.
How to use this tool
- Enter hba1c in the fields above.
- Results update instantly as you type — or click Calculate.
- Read your avg glucose (mg/dl) and the full breakdown beneath it.
Educational estimate — not medical advice. Consult a clinician.
The ADA formula converts HbA1c to estimated average glucose: eAG (mg/dL) = 28.7 × A1C − 46.7. This mirrors the average blood glucose your red blood cells experienced over the past 2–3 months.
Formula
eAG (mg/dL) = 28.7 × A1C (%) − 46.7
eAG (mmol/L) = eAG (mg/dL) ÷ 18.018
This is the ADA consensus equation (Nathan et al., 2008).
How it works
This calculator uses the American Diabetes Association consensus formula to translate HbA1c percentage into an estimated average glucose (eAG), expressed in the same units patients see on their home glucose meters. The linear equation was derived by regressing continuous glucose monitor readings against laboratory HbA1c values across a diverse cohort.
eAG represents an average over the preceding 2–3 months, since red blood cells — and the haemoglobin they carry — live for about 90 days. Individual readings will vary considerably around this average, and the conversion is less reliable in conditions affecting red cell lifespan, such as haemolytic anaemia or iron-deficiency anaemia.
Worked example
Worked example
- Input: HbA1c = 7.0%.
- Apply formula: eAG = 28.7 × 7.0 − 46.7 = 200.9 − 46.7 = 154.2 mg/dL.
- Convert to mmol/L: 154.2 ÷ 18.018 = 8.56 mmol/L.
eAG: 154.2 mg/dL (8.56 mmol/L)
Key terms
- HbA1c (Glycated Haemoglobin)
- A blood marker reflecting average blood glucose over the past 2–3 months; expressed as the percentage of haemoglobin molecules that have glucose attached.
- eAG (Estimated Average Glucose)
- An A1C-derived estimate of mean blood glucose expressed in mg/dL or mmol/L, designed to match the units used by glucose meters.
- ADA consensus formula
- The equation eAG = 28.7 × A1C − 46.7, published by Nathan et al. (2008) and endorsed by the American Diabetes Association.
- mg/dL vs mmol/L
- Two units for blood glucose concentration; the US uses mg/dL while most other countries use mmol/L; conversion factor is 18.018.
- Red blood cell lifespan
- Roughly 90–120 days; because HbA1c accumulates over this period, A1C reflects a 2–3 month glucose average rather than a snapshot.
Frequently asked questions
- What is eAG?
- Estimated average glucose (eAG) translates the HbA1c percentage into mg/dL or mmol/L units familiar from a home glucose meter. It was introduced by the ADA to make A1C results more intuitive.
- Is eAG the same as fasting glucose?
- No. eAG reflects a weighted average over ~3 months including post-meal peaks, not just fasting values. It will typically be higher than a fasting glucose reading.
- What A1C targets do guidelines recommend?
- Most diabetes guidelines recommend A1C below 7% (eAG <154 mg/dL) for most adults with diabetes, though targets are individualised. Speak with your endocrinologist.