Turn an A1C percentage into the estimated average glucose (eAG) you'd see on a meter or CGM — in mg/dL and mmol/L — and convert back the other way. Plain-English normal / prediabetes / diabetes context. Free. No login.
The conversion uses the regression from the A1c-Derived Average Glucose (ADAG) study, which paired A1C with continuous and frequent glucose monitoring across 507 participants. It's the same equation the ADA uses to report eAG.
The prediction interval is wide — one A1C maps to a range of true averages across people. Anemia, hemoglobin variants, pregnancy, recent blood loss, and individual glycation rates shift A1C independent of glucose. If your CGM average and A1C consistently disagree, your A1C is likely biased for you — tell your clinician.
The normal / prediabetes / diabetes bands are ADA screening thresholds. A diagnosis is a clinical decision, usually confirmed with a repeat or second test. Use this to understand a number, not to self-diagnose or change treatment.
Translates A1C and glucose. Not a prescription or a diagnosis. If your result is in the prediabetes or diabetes range, or your A1C and CGM disagree, that's a conversation for a clinician.
eAG translates your A1C into the same units as a glucose meter or CGM — the average blood glucose your A1C corresponds to over roughly the prior 2–3 months. The conversion uses the ADAG regression: eAG (mg/dL) = 28.7 × A1C − 46.7. Divide by 18 for mmol/L.
Per ADA thresholds: below 5.7% is normal, 5.7%–6.4% is prediabetes, and 6.5% or higher (confirmed) is in the diabetes range. These are screening cutoffs — diagnosis is made by a clinician, often with a repeat or confirmatory test.
A1C is an estimate built on a population average and assumes a normal red-blood-cell lifespan. Anemia, recent blood loss, pregnancy, hemoglobin variants, and individual glycation rates can push your A1C above or below what your true glucose average would predict. A CGM measures glucose directly, so a persistent gap usually means your A1C is biased for you specifically — worth flagging to a clinician.
The ADAG regression is a good population estimate, but the prediction interval is wide — a single A1C of 7% maps to an average glucose roughly in the 123–185 mg/dL range across individuals. Use eAG as a translation, not a precise measurement; trend matters more than a single decimal.