A1C to Average Glucose (eAG) Calculator

How it works

HbA1c measures the percentage of your hemoglobin that has glucose attached, reflecting your average blood sugar over roughly the past 2–3 months. Because A1C is a percentage while daily glucose meters read in mg/dL or mmol/L, it helps to convert between them. The A1c-Derived Average Glucose (ADAG) study (Nathan et al., 2008) found a tight linear relationship:

eAG (mg/dL) = 28.7 × A1C − 46.7

To get mmol/L, divide the mg/dL value by 18.0182 (the standard glucose conversion factor). The ADAG study reported that this relationship held across age, sex, diabetes type and race, which is why estimated average glucose (eAG) is now commonly reported alongside A1C on lab results.

The value of eAG is that it puts A1C in the same units as your glucose meter, making the two easier to compare day to day. Remember it is an average: two people with the same A1C can have very different highs and lows around that mean, so eAG complements — but does not replace — self-monitoring and your clinician's interpretation.

Worked example

For an A1C of 7%:

• eAG = 28.7 × 7 − 46.7 = 200.9 − 46.7 = 154.2 mg/dL
• In mmol/L: 154.2 ÷ 18.0182 ≈ 8.6 mmol/L

Each additional 1% of A1C raises the estimated average glucose by 28.7 mg/dL — so 8% ≈ 183 mg/dL and 6% ≈ 126 mg/dL.

Frequently asked questions

What is estimated average glucose (eAG)?

eAG expresses your A1C in the same units as a blood-glucose meter (mg/dL or mmol/L). It is your estimated average blood sugar over the past 2–3 months, calculated from A1C with the ADAG formula.

How do you convert A1C to average glucose?

Use eAG (mg/dL) = 28.7 × A1C − 46.7, then divide by 18.0182 for mmol/L. For A1C 7%, that gives about 154 mg/dL or 8.6 mmol/L.

Why doesn't my meter average match my eAG?

eAG is a modeled average from A1C, not a direct average of your readings. Meter averages depend on when and how often you test, so they often differ from eAG even when both are accurate.

What A1C is considered normal or diabetic?

Generally, below 5.7% is normal, 5.7–6.4% is prediabetes, and 6.5% or higher indicates diabetes, but diagnosis is your clinician's call. This tool only converts A1C to average glucose; it does not diagnose.

Does eAG work for everyone?

The ADAG relationship held across age, sex, diabetes type and race, but individual biology varies — conditions affecting red blood cells can skew A1C. Treat eAG as a useful estimate and confirm interpretation with your provider.

What units should I use?

Most of the US uses mg/dL; many other countries use mmol/L. This calculator shows both, converting with the factor 18.0182 mg/dL per mmol/L.