HbA1c Calculator
HbA1c (glycated hemoglobin) reflects your average blood sugar over the past 2–3 months. This calculator converts between A1c percentage and estimated average glucose (eAG) using the validated ADAG study formula, and provides ADA diabetes classification.
The HbA1c test measures the percentage of hemoglobin in your blood that has glucose attached to it. Since red blood cells live for about 2–3 months, A1c provides a longer-term picture of blood sugar control than a single glucose reading. The A1c-Derived Average Glucose (ADAG) study established the formula eAG (mg/dL) = 28.7 × A1c – 46.7, which is used internationally to convert between A1c and average glucose.
The American Diabetes Association (ADA) uses A1c thresholds for classification: below 5.7% is normal, 5.7–6.4% indicates prediabetes, and 6.5% or higher is consistent with diabetes. For people with diabetes, the ADA generally recommends an A1c target below 7%, though individual targets may vary based on age, health status, and hypoglycemia risk.
Certain conditions can affect A1c accuracy, including hemoglobin variants (sickle cell trait), iron deficiency anemia, kidney disease, and recent blood transfusions. This calculator provides estimates for educational purposes. Always discuss your A1c results with your healthcare provider for proper interpretation and treatment planning.