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A1C calculator
Convert your A1C to an estimated average blood glucose (eAG) — in both mg/dL and mmol/L — or convert average glucose back to an A1C. The calculator uses the American Diabetes Association's ADAG formula and shows where your result falls across the normal, prediabetes, and diabetes ranges.
Estimated average glucose
140mg/dL
≈ 7.8 mmol/L
Diabetes rangeA single A1C is one data point. Vero reads your lab history and Apple Health data together, so it can tell you how your A1C is trending and what's moving it.
Understand your A1C with VeroA1C to average glucose chart
A1C measures the percentage of your hemoglobin coated in sugar, reflecting your average blood glucose over the previous 2–3 months. The estimated average glucose (eAG) puts that number into the mg/dL units you see on a glucose meter. Here's how the standard diagnostic ranges line up:
| A1C | Estimated average glucose | Category |
|---|---|---|
| Below 5.7% | Below 117 mg/dL (6.5 mmol/L) | Normal |
| 5.7% – 6.4% | 117–137 mg/dL (6.5–7.6 mmol/L) | Prediabetes |
| 6.5% or higher | 140 mg/dL (7.8 mmol/L) and up | Diabetes |
Diabetes is diagnosed at an A1C of 6.5% or higher, typically confirmed on a second test. Reference ranges and personal targets vary — always use the interpretation on your own lab report and your clinician's guidance.
The formula
The conversion comes from the A1C-Derived Average Glucose (ADAG) study:
To convert mg/dL to mmol/L, divide by 18.0182. The calculator reverses the same equation when you enter an average glucose to estimate the matching A1C.
Frequently asked questions
How do you convert A1C to average blood sugar?
Use the ADA-endorsed ADAG formula: estimated average glucose (mg/dL) = 28.7 × A1C − 46.7. For example, an A1C of 6.5% works out to about 140 mg/dL (7.8 mmol/L). To get mmol/L, divide the mg/dL value by 18.0182. The calculator above does both directions for you.
What is a normal A1C level?
For most adults without diabetes, an A1C below 5.7% is considered normal. 5.7–6.4% falls in the prediabetes range, and 6.5% or higher on two tests is used to diagnose diabetes. Targets are individualized — many people with diabetes aim for under 7%, but your doctor may set a different goal based on age and health.
What is estimated average glucose (eAG)?
eAG translates your A1C into the same mg/dL (or mmol/L) units you see on a home glucose meter, making the number easier to relate to daily readings. It reflects your average blood sugar over roughly the previous 2–3 months, not a single moment.
Why doesn't my A1C match my daily glucose readings?
A1C is a 2–3 month average, so it can differ from recent meter readings. It can also be skewed by conditions that change red blood cell lifespan — anemia, recent blood loss or transfusion, pregnancy, and certain hemoglobin variants — which make the eAG estimate less reliable. Discuss any mismatch with your doctor.
How much can A1C change in 3 months?
Because A1C reflects roughly 3 months of average glucose, meaningful change shows up over that window. With consistent diet, activity, and medication changes, drops of 0.5–1.0 percentage points over 3 months are common, and larger drops are possible from higher starting points. Rapid, very large drops should be supervised by a clinician.
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Medically reviewed by Antonieta Rueda, MD and Kyle R. Toth, MD · Last reviewed July 6, 2026
This calculator provides general estimates for informational purposes only and is not a substitute for personalized advice from a doctor. The A1C-to-glucose conversion is an estimate and may be less accurate in anemia, pregnancy, recent blood loss, and certain hemoglobin variants. Diabetes should be diagnosed and managed by a clinician.