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Health & Body
A1C Calculator — Convert A1C to Average Blood Sugar (eAG)
See what your A1C percentage means in everyday mg/dL blood sugar numbers
Your A1C (also written HbA1c) is a single number that sums up your average blood sugar over the past two to three months. It's reported as a percentage — the share of your hemoglobin that has glucose stuck to it. The higher your average blood sugar, the higher that percentage climbs. The problem is that an A1C like 6.5% doesn't feel like anything, because the glucose meter you check at home reads in mg/dL — numbers like 120 or 154. This calculator bridges the two.
The American Diabetes Association uses a simple linear relationship to translate A1C into an estimated average glucose (eAG):
eAG (mg/dL) = 28.7 × A1C − 46.7
To go the other way — turning a meter average into an A1C estimate — flip it around:
A1C (%) = (eAG + 46.7) ÷ 28.7
Worked example. Say your A1C is 7.0%. Then eAG = 28.7 × 7.0 − 46.7 = 200.9 − 46.7 = 154 mg/dL. So a 7% A1C lines up with an average blood sugar around 154 mg/dL — a number you can compare directly to your meter readings.
The categories most US clinicians use: normal is below 5.7%, prediabetes is 5.7% to 6.4%, and diabetes is 6.5% or higher (confirmed on a repeat test). For many adults already living with diabetes, a common A1C goal is under 7%, but targets are personal — your doctor may set a higher or lower number based on your age, history and other conditions.
The common mistake: treating eAG as if it were a single fasting reading. It is not. eAG is an average across day and night, before and after meals — so it will usually sit higher than your fasting number and lower than your post-meal spikes. A normal-looking eAG can still hide big swings.
This tool is informational only and is not medical advice. It gives an estimate, not a diagnosis. Only a lab test ordered and interpreted by your healthcare provider can confirm your A1C — always discuss your results with a doctor before changing anything.
📖 See also: Body Fat Percentage: How to Measure It at Home
Calculator
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📰 Formula
• eAG (mg/dL) = 28.7 × A1C − 46.7 • A1C (%) = (eAG + 46.7) ÷ 28.7 • Normal: A1C < 5.7% • Prediabetes: A1C 5.7% – 6.4% • Diabetes: A1C ≥ 6.5% (confirmed on a repeat test)
📰 Formula
• eAG (mg/dL) = 28.7 × A1C − 46.7 • A1C (%) = (eAG + 46.7) ÷ 28.7 • Normal: A1C < 5.7% • Prediabetes: A1C 5.7% – 6.4% • Diabetes: A1C ≥ 6.5% (confirmed on a repeat test)
🧪 Worked examples
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Example 4
⚠️ Common mistakes
- Reading eAG as a single fasting value — it is an average across the whole day.
- Mixing up the direction: eAG comes from A1C, not the reverse, unless you start from a glucose average.
- Entering a glucose reading in mmol/L instead of mg/dL (multiply mmol/L by 18 first).
- Assuming a low eAG rules out diabetes — high and low swings can average out.
💡 Tips
- Compare the eAG to your meter's day-and-night average, not to a single morning reading.
- A1C below 5.7% is normal, 5.7–6.4% is prediabetes, and 6.5% or higher is the diabetes range.
- Use this estimate to frame questions for your doctor — never to self-diagnose or change treatment.
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❓ Frequently asked questions
What does my A1C mean in blood sugar numbers?
A1C converts to an estimated average glucose (eAG) with eAG = 28.7 × A1C − 46.7. So a 6.5% A1C is about 140 mg/dL, and a 7% A1C is about 154 mg/dL — your average blood sugar over the last 2–3 months.
What is a normal A1C level?
In the US, an A1C below 5.7% is considered normal. From 5.7% to 6.4% is prediabetes, and 6.5% or higher (confirmed on a repeat test) is in the diabetes range.
What A1C is diabetes?
An A1C of 6.5% or above, confirmed on a second test, meets the diabetes threshold used by the American Diabetes Association. Diagnosis is always made by a healthcare provider, not by a calculator.
What A1C is prediabetes?
An A1C between 5.7% and 6.4% is the prediabetes range. It means average blood sugar is higher than normal but not yet in the diabetes range — a signal to talk with your doctor about prevention.
How do I convert eAG back to A1C?
Use A1C = (eAG + 46.7) ÷ 28.7. For example, an average glucose of 154 mg/dL gives (154 + 46.7) ÷ 28.7 ≈ 7.0% A1C.
Is eAG the same as my fasting blood sugar?
No. eAG is an average across the entire day and night, including after meals. It will usually read higher than a fasting number and lower than a post-meal spike, so don't compare it to a single reading.
What is a good A1C goal for someone with diabetes?
Many adults aim for under 7%, but goals are individual — your doctor may set a higher or lower target based on your age, how long you've had diabetes, and other health conditions.
How often should A1C be checked?
Typically every 3 months if you're adjusting treatment or above target, and about every 6 months if you're stable and at goal. Your provider will tell you the right schedule for you.
Can this calculator diagnose diabetes?
No. This tool is informational only and is not medical advice. It gives an estimate from a formula. Only a lab test ordered and interpreted by your doctor can confirm an A1C or diagnose diabetes.