A1C (HbA1c) is a percentage that reflects your average blood glucose over about 2–3 months. This tool converts it to estimated average glucose (eAG) using the ADAG formula — eAG mg/dL = 28.7 × A1C − 46.7 — and back again, and shows where the A1C falls among the normal, prediabetes and diabetes bands.
Reviewed: June 20, 2026 · Author: Naveen P N, Founder — AI Calculator · Verified against: the ADAG eAG equations, recomputed in code. Educational only, not medical advice.
The conversion formulas
These come from the international ADAG study, which related lab A1C to continuously-measured average glucose. The mg/dL and mmol/L lines are the same relationship in the two glucose units. Standard A1C bands are below 5.7% normal, 5.7–6.4% prediabetes, and 6.5% or higher in the diabetes range.
Worked examples
A1C of 7%:
A1C of 5.7% (prediabetes threshold):
Average glucose of 154 mg/dL back to A1C:
So an A1C of 7% corresponds to an average glucose around 154 mg/dL, and 6.5% — the diabetes threshold — to about 140 mg/dL. Remember eAG is a long-run average, not a snapshot from a meter.
Frequently Asked Questions
eAG mg/dL = 28.7 × A1C − 46.7; mmol/L = 1.59 × A1C − 2.59. A1C 7% ≈ 154 mg/dL (8.5 mmol/L).
Bands: <5.7% normal, 5.7–6.4% prediabetes, ≥6.5% diabetes range. A clinician makes the diagnosis.
No. eAG is a 2–3 month average from A1C; a glucometer is one moment that swings with meals and time.
A1C = (mg/dL + 46.7) / 28.7. 154 mg/dL ≈ 7%. An estimate, not a lab test.
About the prior 2–3 months, since red cells live that long. It smooths out daily swings.