A1C Calculator: Convert Your A1C to Average Blood Sugar

Reviewed by the JForH team · 2026-10-30

To turn A1C into estimated average blood sugar (eAG), multiply your A1C by 28.7 and subtract 46.7; the answer is in mg/dL. An A1C of 7% equals an average of about 154 mg/dL (8.5 mmol/L), and 6% equals about 126 mg/dL (7.0 mmol/L). This formula comes from the ADAG study (Nathan et al., Diabetes Care, 2008).

How do you convert A1C to average blood sugar?

Your A1C can be turned into an estimated average glucose, or eAG. This is the same kind of number you see on a home glucose meter. The formula comes from the A1C-Derived Average Glucose (ADAG) study, which compared A1C with frequent finger-stick and continuous glucose readings in 507 adults.

• In mg/dL (used in the US): eAG = 28.7 × A1C − 46.7
• In mmol/L (used in many other countries): eAG = 1.59 × A1C − 2.59

Example: an A1C of 8% gives 28.7 × 8 − 46.7 = 182.9, so your average blood sugar is about 183 mg/dL. Use the calculator on this page, or find your number in the chart below.

The eAG is an estimate. In the ADAG study, two people with the same A1C could have somewhat different true averages. Treat it as a guide, not an exact reading.

A1C to average blood sugar chart (5% to 12%)

Each row uses the ADAG formula. Average blood sugar in mg/dL is rounded to a whole number; mmol/L is rounded to one decimal place.

A quick rule of thumb from the chart: each 1-point change in A1C is about a 29 mg/dL (1.6 mmol/L) change in average blood sugar.

What does A1C measure?

A1C is a blood test that shows the share of your hemoglobin, the protein in red blood cells that carries oxygen, that has sugar attached to it. The more sugar in your blood over time, the higher the percentage. Because red blood cells live for a few months, A1C reflects your average blood sugar over roughly the past 3 months, according to the NIDDK. The CDC describes it as the past 2 or 3 months.

You do not need to fast for an A1C test. It is reported as a percentage (for example, 6.8%) and sometimes also in mmol/mol.

What is a normal A1C?

For adults, the American Diabetes Association (ADA) and the CDC use these ranges to diagnose prediabetes and diabetes:

The average blood sugar column is calculated from the ADAG formula and is shown only to help you picture the numbers. Diagnosis is made on the A1C result itself, not the eAG.

What A1C is considered prediabetes?

An A1C from 5.7% to 6.4% is in the prediabetes range. It means your blood sugar is higher than normal but not high enough to be called diabetes. The ADA notes that risk rises across this range and climbs faster toward the top of it, so 6.2% carries more risk than 5.8%. Prediabetes is a useful warning: changes to eating, activity and weight can lower the chance of moving on to type 2 diabetes.

What A1C means diabetes?

An A1C of 6.5% or higher is in the diabetes range. The ADA says that unless you have clear symptoms of very high blood sugar, the result should be confirmed with a second test, either a repeat A1C or a different test such as fasting plasma glucose.

What should my A1C goal be?

For many adults with diabetes who are not pregnant, the ADA says an A1C goal below 7% is appropriate. That is an average blood sugar of about 154 mg/dL. Goals are set person by person. A lower goal may suit some people if it can be reached safely, without low blood sugar. A higher goal may suit others.

A1C goals for older adults

The ADA Standards of Care section on older adults suggests goals based on overall health, not age alone:

The reason for looser goals is safety. Low blood sugar can cause falls, confusion and hospital visits, and older adults are more likely to have them. Talk with your care team about the goal that fits you.

What can make an A1C result wrong?

A1C depends on how long red blood cells live. Anything that changes that can make the result read too high or too low. The ADA and NIDDK list:

• Anemia. Iron-deficiency anemia can make A1C read falsely high. Other anemias, such as hemolytic anemia, can also throw it off.
• Kidney failure and dialysis, and treatment with erythropoietin (a medicine that boosts red blood cells).
• Recent blood loss or a blood transfusion.
• Pregnancy, because red blood cells turn over faster. A1C is not used to diagnose diabetes that starts in pregnancy.
• Some hemoglobin variants, such as sickle cell trait or thalassemia, which are more common in people of African, Mediterranean or Southeast Asian ancestry. With some lab methods these can affect results. A1C cannot be used at all in people with sickle cell disease.
• Liver disease.

If your A1C does not match your meter or sensor readings, tell your doctor. A fasting glucose test or a continuous glucose monitor (CGM) can give a clearer picture.

A1C vs. CGM GMI: what is the difference?

A CGM is a small sensor worn on the skin that checks sugar every few minutes. CGM reports often show a Glucose Management Indicator, or GMI. GMI works the other way around from eAG: it starts with your average sensor glucose and estimates what your A1C would be. The formula, from Bergenstal and colleagues (Diabetes Care, 2018), is GMI (%) = 3.31 + 0.02392 × average glucose in mg/dL. The ADA suggests looking at about 14 days of CGM data for these reports.

GMI and a lab A1C often differ by a few tenths of a point, and sometimes more. That does not mean either one is wrong. The ADA describes GMI as an approximation of A1C that is not always equivalent. A CGM also shows things A1C cannot, such as time in range (the share of the day spent between 70 and 180 mg/dL), lows overnight and spikes after meals. For many adults with diabetes, the goal is more than 70% time in range, per the International Consensus on Time in Range and the ADA.

How often should A1C be checked?

The ADA recommends checking glycemic status, usually with A1C, at least twice a year if you are meeting your goals, and more often, such as every 3 months, if you are not meeting your goal or your treatment recently changed. People without diabetes are screened less often; the CDC suggests an A1C test for adults over 45, and younger adults with overweight and another risk factor.

What to do with your number

• Below 5.7%: keep up healthy habits and follow your doctor's screening schedule.
• 5.7% to 6.4%: ask about a lifestyle program for prediabetes and when to recheck.
• 6.5% or higher, and no diagnosis yet: see your doctor to confirm the result with a second test.
• Already living with diabetes: compare your A1C with the goal you set with your care team, and look at your daily readings or CGM report for patterns.

This calculator is for education. It does not diagnose diabetes or replace advice from your doctor.

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Last updated: 2026-10-30. Educational information, not medical advice. Talk to your doctor before changing your treatment.