A1C calculator: convert A1C to average blood sugar (eAG)

An A1C of 6% equals an estimated average glucose (eAG) of about 126 mg/dL (7.0 mmol/L), and an A1C of 7% equals about 154 mg/dL (8.6 mmol/L). The conversion uses the ADAG study formula: eAG (mg/dL) = 28.7 × A1C − 46.7.

Last reviewed: September 30, 2026

A1C calculator

The A1C to eAG formula

eAG (mg/dL) = 28.7 × A1C − 46.7

eAG (mmol/L) = 1.5944 × A1C − 2.594

The formula comes from the A1c-Derived Average Glucose (ADAG) study (Nathan et al., 2008). Researchers compared A1C with about 2,700 glucose readings per person over 3 months, from continuous glucose monitoring plus fingersticks, in 507 people with type 1 diabetes, type 2 diabetes or no diabetes at 10 international centers. The straight-line fit was tight (R² = 0.84) and did not differ by age, sex, diabetes type, race/ethnicity or smoking.

The mmol/L version is often quoted rounded as 1.59 × A1C − 2.59; we use the study's unrounded coefficients, which reproduce its published table exactly. To go the other way, A1C = (eAG in mg/dL + 46.7) ÷ 28.7. Results are rounded to whole mg/dL, one decimal in mmol/L and one decimal for A1C, and the range label is based on the rounded A1C.

A1C to average glucose chart

A1C and estimated average glucose (ADAG formula), with ADA/CDC ranges
A1C	eAG (mg/dL)	eAG (mmol/L)	Range
5.0%	97	5.4	Normal range
5.5%	111	6.2	Normal range
5.7%	117	6.5	Prediabetes range
6.0%	126	7.0	Prediabetes range
6.5%	140	7.8	Diabetes range
7.0%	154	8.6	Diabetes range
7.5%	169	9.4	Diabetes range
8.0%	183	10.2	Diabetes range
8.5%	197	11.0	Diabetes range
9.0%	212	11.8	Diabetes range
9.5%	226	12.6	Diabetes range
10.0%	240	13.4	Diabetes range
11.0%	269	14.9	Diabetes range
12.0%	298	16.5	Diabetes range

What your result means

Normal: A1C below 5.7%.
Prediabetes: A1C 5.7–6.4%.
Diabetes range: A1C 6.5% or above.

These are the CDC and American Diabetes Association cut-offs. eAG is an estimate: in the ADAG study, people with the same A1C had a spread of real average glucose (for an A1C of 7%, roughly 123–185 mg/dL). Anemia, kidney or liver disease, some blood disorders, blood loss or transfusions, certain medicines and pregnancy can all shift A1C, so an A1C outside the normal range is something to discuss with your doctor rather than a diagnosis on its own.

Frequently asked questions

How do you convert A1C to average blood sugar?

Use the ADAG formula: estimated average glucose (mg/dL) = 28.7 × A1C − 46.7, or in mmol/L, 1.59 × A1C − 2.59. For example, an A1C of 8% gives 28.7 × 8 − 46.7 ≈ 183 mg/dL (10.2 mmol/L).

What A1C is normal, prediabetes or diabetes?

According to the CDC and the American Diabetes Association, an A1C below 5.7% is normal, 5.7% to 6.4% is prediabetes, and 6.5% or above is in the diabetes range. Only your doctor can diagnose prediabetes or diabetes.

Is eAG the same as my fasting blood sugar?

No. eAG estimates your average glucose around the clock over roughly the past 3 months, including after meals and overnight, so it won't match a fasting reading or any single fingerstick.

Why doesn't my A1C match my meter or CGM average?

The ADAG formula describes the average relationship across many people. In the study, an A1C of 7% corresponded to average glucose anywhere from 123 to 185 mg/dL (95% range). The CDC also lists conditions that can make A1C read falsely high or low, including severe anemia, kidney failure, liver disease, sickle cell anemia or thalassemia, blood loss or transfusions, some medicines, and early or late pregnancy.

Can I calculate my A1C from my average glucose?

Yes. Switch the calculator to "Average glucose → A1C". It reverses the ADAG formula: A1C = (average glucose in mg/dL + 46.7) ÷ 28.7. For example, an average of 154 mg/dL corresponds to an A1C of about 7.0%.