HbA1c to eAG Calculator
Convert HbA1c percentage to estimated Average Glucose (eAG) in mg/dL and mmol/L using the ADA formula.
Includes interpretation and diabetes risk ranges.
What Is HbA1c? HbA1c (glycated hemoglobin, also called A1C) is a blood test that reflects your average blood glucose level over the past 2–3 months. Red blood cells live roughly 90 days, and glucose gradually attaches to hemoglobin during that time. The higher your blood sugar, the more glycated hemoglobin accumulates — giving doctors a reliable long-term picture of glucose control.
The ADA eAG Formula (Nathan et al. 2008) The American Diabetes Association formula for converting HbA1c to estimated Average Glucose (eAG): eAG (mg/dL) = 28.7 × HbA1c(%) − 46.7 eAG (mmol/L) = eAG(mg/dL) ÷ 18.0182
This formula was derived from continuous glucose monitoring data across thousands of patients in the ADAG study. It is more clinically meaningful than HbA1c % alone because patients can relate to daily glucose numbers.
Worked Example HbA1c = 7.0% eAG = 28.7 × 7.0 − 46.7 = 200.9 − 46.7 = 154.2 mg/dL eAG = 154.2 ÷ 18.0182 ≈ 8.6 mmol/L
Clinical Interpretation < 5.7% — Normal (no diabetes diagnosis) 5.7% – 6.4% — Pre-diabetes (impaired glucose tolerance) ≥ 6.5% — Diabetes range (diagnostic threshold) ADA target for most adults with diabetes: < 7% (eAG < 154 mg/dL / 8.6 mmol/L) More stringent target (younger, no complications): < 6.5% Less stringent target (elderly, comorbidities): < 8%
Important Limitations HbA1c can be falsely low in hemolytic anemia, sickle cell disease, or iron deficiency. It can be falsely high in iron deficiency anemia or certain hemoglobin variants. The eAG formula applies to adults and is an estimate — not a direct glucose measurement. Always consult a healthcare provider for diagnosis and treatment decisions.