A1C to Glucose Calculator
Convert HbA1c and estimated average glucose using ADAG.
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This calculator gives a general estimate and isn't medical advice. It doesn't account for your individual health history — talk to a doctor before making decisions based on it.
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Formula
eAG (mg/dL) = 28.7 × HbA1c − 46.7
The ADAG study linked HbA1c — glycated haemoglobin over ~3 months — to average blood glucose. The inverse formula estimates A1c from a reported average glucose for comparison, though lab A1c remains the clinical standard.
Worked example
An HbA1c of 6.5% maps to an estimated average glucose of about 140 mg/dL (7.8 mmol/L) — the ballpark clinicians use when discussing 'what that A1c means' in daily numbers.
Where this can give the wrong answer
- Anaemia, haemoglobin variants, and recent transfusion can skew HbA1c independently of average glucose.
- The ADAG line is a population fit — individual CGM averages may diverge by 10–15 mg/dL from the estimate.
- Prediabetes and diabetes thresholds differ by country; this tool converts numbers, it doesn't diagnose.
FAQ
- Many guidelines use below 5.7% as typical, 5.7–6.4% as prediabetes range, and 6.5% or higher on repeat testing as diabetes range — always confirm with a clinician and lab standards in your region.