This free A1c calculator converts your HbA1c into your estimated average blood sugar (in mg/dL and mmol/L) and into IFCC units (mmol/mol), or works the other way round from an average glucose. It uses the equation from the international ADAG study and shows where your result falls in the American Diabetes Association categories.
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What is A1c?
HbA1c (A1c) measures how much sugar is stuck to your red blood cells. Because red blood cells live about 3 months, it reflects your average blood sugar over the past 2 to 3 months, which is why it is used to screen for prediabetes and diabetes.
A1c to average blood sugar chart
| A1c | mmol/mol | Estimated average glucose |
|---|---|---|
| 5% | 31 | 97 mg/dL (5.4 mmol/L) |
| 5.7% | 39 | 117 mg/dL (6.5 mmol/L) |
| 6% | 42 | 126 mg/dL (7.0 mmol/L) |
| 6.5% | 48 | 140 mg/dL (7.8 mmol/L) |
| 7% | 53 | 154 mg/dL (8.6 mmol/L) |
| 8% | 64 | 183 mg/dL (10.2 mmol/L) |
| 9% | 75 | 212 mg/dL (11.7 mmol/L) |
| 10% | 86 | 240 mg/dL (13.3 mmol/L) |
Average glucose = 28.7 × A1c − 46.7 (ADAG study, Diabetes Care 2008). mmol/mol = 10.929 × (A1c − 2.15).
What your A1c means (ADA categories)
| A1c | Category |
|---|---|
| under 5.7% | Normal |
| 5.7% to 6.4% | Prediabetes |
| 6.5% or higher | Diabetes range (needs a second test to confirm) |
The American Diabetes Association recommends screening all adults from age 35, and earlier for people with overweight and other risk factors, repeating at least every 3 years if results are normal.
Can prediabetes be reversed?
Often, yes. In the Diabetes Prevention Program, a lifestyle program for people with prediabetes that aimed for 7% weight loss and 150 minutes of activity a week cut the risk of developing diabetes by 58% over about 3 years. Walking after meals, strength training and keeping your waist under half your height all help. Check your waist-to-height ratio and your metabolic age.
When A1c can be misleading
- Anemia, iron deficiency, recent blood loss or transfusion
- Some hemoglobin variants, such as sickle cell trait
- Advanced kidney disease, pregnancy and some HIV medicines
A1c calculator FAQ
What is a normal A1c?
Under 5.7% is normal for people without diabetes, according to the American Diabetes Association.
What A1c is prediabetes?
An A1c from 5.7% to 6.4% is in the prediabetes range. It means a higher risk of type 2 diabetes and heart disease, and it is often reversible.
How accurate is estimated average glucose?
It is an estimate. In the ADAG study the typical difference between estimated and real average glucose was about 16 mg/dL (0.9 mmol/L).
What A1c should I aim for if I have diabetes?
Many adults with diabetes aim for under 7%, but your doctor may set a higher or lower goal depending on your health and risk of low blood sugar.
This calculator is for education, not diagnosis, and does not replace advice from your doctor. Last reviewed: October 28, 2026. See our medical disclaimer.
Sources
- Nathan DM et al. Translating the A1C Assay Into Estimated Average Glucose Values. Diabetes Care, 2008
- American Diabetes Association. Standards of Care in Diabetes, 2026: Diagnosis and Classification
- Knowler WC et al. Reduction in the Incidence of Type 2 Diabetes with Lifestyle Intervention or Metformin. N Engl J Med, 2002
