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A1C Calculator

Your A1C test (also called HbA1c or glycated hemoglobin) reflects your average blood sugar over the past 2–3 months. This calculator uses the ADAG (A1C-Derived Average Glucose) formula — validated in a landmark 2008 multinational study — to translate your A1C into an estimated average glucose (eAG) value, expressed in the same mg/dL or mmol/L units you see on your glucose meter. You can also enter an average glucose reading to back-calculate your approximate A1C.

Reviewed by GetHealthyCalculators Editorial Team · Updated April 5, 2026

Quick Answer

An A1C of 6.0% equals an estimated average glucose of about 126 mg/dL (7.0 mmol/L). Use the ADAG formula: eAG = 28.7 × A1C − 46.7.

These results are estimates based on general formulas and are not a substitute for professional medical advice. Consult a healthcare provider before making health decisions.

Conversion Direction

Enter a value between 4.0% and 20.0%

Enter your A1C percentage to see your estimated average glucose.

How the Formula Works

  1. Start with your A1C percentage (e.g., 6.5).

    A1C = 6.5%

  2. Multiply A1C by 28.7 to get the first part of the conversion.

    28.7 × 6.5 = 186.55

  3. Subtract 46.7 to obtain estimated average glucose in mg/dL.

    eAG (mg/dL) = 28.7 × A1C − 46.7 = 186.55 − 46.7 = 139.9 ≈ 140 mg/dL

  4. To convert eAG from mg/dL to mmol/L, divide by 18.

    eAG (mmol/L) = 140 ÷ 18.0 ≈ 7.8 mmol/L

  5. To reverse-calculate A1C from an average glucose, rearrange the formula.

    A1C (%) = (eAG + 46.7) ÷ 28.7

Methodology & Sources

Reviewed and updated April 5, 2026 · Prepared by GetHealthyCalculators Editorial Team

This calculator implements the ADAG formula published by Nathan et al. (2008) and endorsed by the ADA and AHA. The formula was derived from continuous glucose monitoring data in 507 adults with type 1 and type 2 diabetes across 10 countries. It provides a statistically validated translation between A1C and average glucose, with an R² of 0.84.

References

Limitations

  • The ADAG formula estimates an average glucose — individual day-to-day readings will vary significantly above and below this estimate.
  • A1C can be falsely low or high in conditions that affect red blood cell lifespan, such as hemolytic anemia, sickle cell disease, pregnancy, or recent blood transfusion.
  • The ADAG study included adults only; results may be less accurate in children with diabetes.
  • This tool is for informational purposes only and does not constitute a diagnosis. A1C diagnosis requires a confirmatory clinical lab test.
  • If you have chronic kidney disease, hemoglobin variants, or other conditions, your healthcare provider may prefer alternative glycemic assessments.

Frequently Asked Questions

What is A1C and why does it matter?
A1C (glycated hemoglobin or HbA1c) measures the percentage of hemoglobin coated with glucose. Because red blood cells live about 3 months, A1C reflects your average blood sugar over that period, making it a more reliable long-term marker than a single fasting glucose test. It is used both to diagnose diabetes and to monitor how well blood sugar is managed in people already diagnosed.
What is a normal A1C level?
According to the ADA, a normal A1C is below 5.7%. Values between 5.7% and 6.4% indicate prediabetes, and 6.5% or higher on two separate tests confirms a diabetes diagnosis. For people already managing diabetes, the ADA generally recommends keeping A1C below 7.0%, though individualized targets are set by a healthcare provider.
What is the ADAG formula?
The ADAG formula (eAG = 28.7 × A1C − 46.7) was derived in a 2008 multinational study led by Dr. David Nathan. Researchers matched A1C readings with continuous glucose monitoring data from 507 adults to create a statistically reliable translation between A1C and estimated average glucose (eAG). The ADA now uses eAG on lab reports to make A1C more intuitive for patients.
What is estimated average glucose (eAG)?
Estimated average glucose (eAG) converts your A1C result into the same mg/dL or mmol/L units shown on a standard glucose meter. Because most people check their blood sugar in mg/dL or mmol/L, expressing A1C as eAG makes it easier to understand — for example, an A1C of 7.0% equals an eAG of about 154 mg/dL (8.6 mmol/L).
Can A1C be inaccurate?
Yes. A1C can be falsely low in conditions where red blood cells are destroyed faster than normal (e.g., hemolytic anemia, sickle cell disease, or after a blood transfusion). It can be falsely high in iron-deficiency anemia. Pregnancy can also affect A1C. If you have any of these conditions, your doctor may rely on fructosamine, continuous glucose monitoring, or other tests instead.
How often should A1C be tested?
For adults without diabetes who are at risk, the ADA recommends testing at least every 3 years (or more frequently if risk factors change). For people with type 2 diabetes who are meeting treatment goals and have stable glycemic control, the ADA recommends testing at least twice per year. People with type 1 diabetes or those whose treatment has recently changed should test every 3 months.
Is an A1C of 6.0% considered normal?
An A1C of 6.0% falls within the prediabetes range (5.7–6.4%), meaning blood sugar is higher than ideal but not yet at the diabetes threshold. The estimated average glucose at 6.0% is approximately 126 mg/dL (7.0 mmol/L). Many people at this level can return to the normal range with consistent lifestyle changes such as a healthier diet, regular exercise, and weight management.
What A1C target should I aim for if I have diabetes?
The ADA generally recommends an A1C below 7.0% for most non-pregnant adults with diabetes, as this level balances glycemic control with minimizing hypoglycemia risk. However, individualized targets may be higher (e.g., 8.0%) for older adults or those with frequent hypoglycemia, and tighter (e.g., 6.5%) for younger people with short disease duration and no cardiovascular disease. Always work with your healthcare team to set a personal target.

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