A1C Calculator — A1C to eAG Conversion

A1C Calculator

How to Use A1C Calculator — A1C to eAG Conversion

1. Step 1: Choose Conversion

   Pick “A1C → eAG” to convert your A1C to an average glucose, or “eAG → A1C” if you want to estimate A1C from a known average.

2. Step 2: Enter Value & Units

   Type your A1C (%) or eAG and select mg/dL or mmol/L. Inputs are mobile‑friendly and accept decimals.

3. Step 3: Calculate

   Tap Calculate to see eAG in mg/dL and mmol/L plus your A1C and category (normal, prediabetes, diabetes).

4. Step 4: Review & Save

   Compare your result to thresholds, then screenshot or note it for your records. Use Related Calculators for deeper context.

Key Features

• A1C → eAG and eAG → A1C
• Normal, prediabetes, diabetes thresholds
• Dual units: mg/dL and mmol/L
• Mobile‑first inputs with copy‑friendly results

Understanding Results

A1C Calculator Formula

This tool uses the ADAG relationship to convert between A1C and estimated average glucose (eAG). In plain English: multiply your A1C (%) by 28.7 and subtract 46.7 to get eAG in mg/dL. To see mmol/L, divide that eAG by 18. Working backward, you can estimate A1C by adding 46.7 to your average glucose (mg/dL) and dividing by 28.7. The calculator supports both directions.

Using the A1C Calculator

Enter your values carefully and choose the correct units. Compare your result with the listed thresholds, and discuss your targets with your clinician. This calculator provides educational estimates and does not replace personalized medical guidance.

Reference Ranges & Interpretation

Common thresholds are: Normal below 5.7% (≈ <117 mg/dL or 6.5 mmol/L), Prediabetes 5.7–6.4% (≈ 117–137 mg/dL or 6.5–7.6 mmol/L), and Diabetes (by A1C) 6.5% or higher (≈ ≥140 mg/dL or ≥7.8 mmol/L). Your targets may differ depending on age, medications, risk of hypoglycemia, and other health considerations. Use these ranges as a conversation starter with your clinician rather than a diagnosis.

Assumptions & Limitations

A1C reflects the average glucose attached to red blood cells over roughly 2–3 months. Anything that changes red blood cell lifespan or hemoglobin type can shift A1C without matching your day‑to‑day readings. Examples include certain anemias, pregnancy, kidney or liver disease, recent blood loss or transfusion, and hemoglobin variants. In such cases your clinician may rely more on glucose logs, fructosamine, or CGM reports. Results here are estimates only and are not medical advice.

Complete Guide: A1C Calculator — A1C to eAG Conversion

Use our A1C calculator to convert HbA1c to estimated average glucose (eAG). See normal, prediabetes, and diabetes thresholds in mg/dL and mmol/L. Fast results.

This guide pairs the calculator with practical context. You will learn what A1C represents, how the eAG conversion works, how to interpret normal, prediabetes, and diabetes ranges, and what can make results differ from finger‑stick or CGM readings. The tone stays plain and useful — not medical advice — so you can discuss results with your clinician from a more informed position.

What is A1C and why it matters

A1C (also written HbA1c or glycated hemoglobin) reflects how much glucose has attached to red blood cells over their lifespan. Because red blood cells circulate for roughly three months, A1C acts like a rolling average of your blood glucose during the past 8–12 weeks. Many clinicians use A1C to diagnose diabetes, track long‑term control, and guide treatment decisions. Unlike a single glucose reading, it smooths out the day‑to‑day ups and downs and captures the bigger picture.

Our A1C calculator translates a percentage into estimated average glucose (eAG). If A1C feels abstract — say, 6.8% — eAG puts it in familiar units: mg/dL in the United States or mmol/L in many other countries. That’s helpful when you want to compare lab results with home readings or align goals with what you see on a meter or blood sugar calculator.

The A1C → eAG formula explained

The conversion most commonly used comes from the ADAG study: eAG (mg/dL) = 28.7 × A1C − 46.7. It expresses the average glucose that corresponds to a given A1C. To see results in mmol/L, divide the eAG in mg/dL by 18. The inverse equation — useful if you start from an average glucose — is A1C = (eAG in mg/dL + 46.7) ÷ 28.7. The tool handles both directions and displays mg/dL and mmol/L together so you can think in your preferred unit.

Here’s a quick example. Suppose your lab reports an A1C of 6.8%. Multiply 6.8 by 28.7 to get 195.16, then subtract 46.7 to get an eAG of about 148 mg/dL. To see the same number in mmol/L, divide by 18: 148 ÷ 18 ≈ 8.2 mmol/L. If you measure your own average with a meter or CGM and it comes out near those values, you’ll see why the A1C and the average “agree.” If they differ, that tells you to dig deeper into daily patterns or special cases (see below).

Because A1C captures a long window, two people can share the same A1C but have very different experiences: one stays steady around the average, another bounces between highs and lows that cancel out. That’s why the calculator is designed to coexist with other tools rather than replace them. It gives a clean, comparable average that you can place alongside CGM time‑in‑range, fasting values, and post‑meal checks.

Remember that these are estimates based on population data. Two people with the same A1C could have different daily patterns — one may stay steady, another may swing from high to low. That’s why you read A1C alongside daily measurements or CGM trends rather than in isolation.

Interpreting A1C and eAG in daily life

Treat the A1C and eAG from the calculator as a dashboard value — it summarizes recent months, not yesterday’s choices. If your eAG looks higher than your meter or CGM suggests, check whether recent weeks included illness, medication changes, or periods of higher readings. If your daily data looks smoother but the A1C is still elevated, discuss time‑in‑range, hypoglycemia risk, and individualized targets with your care team. Use the tool to translate between an abstract percentage and everyday numbers you can act on.

Ranges: normal, prediabetes, diabetes

Commonly used thresholds are straightforward: Normal is below 5.7%, Prediabetes is 5.7–6.4%, and Diabetes (by A1C) is 6.5% or higher. When converted to eAG, that’s roughly below 117 mg/dL (6.5 mmol/L) for normal, about 117–137 mg/dL (6.5–7.6 mmol/L) for prediabetes, and 140 mg/dL (7.8 mmol/L) or above for diabetes. Your care plan may target different goals depending on age, pregnancy, medications, duration of diabetes, risk of lows, and other conditions.

What do these ranges mean day to day? They provide guardrails rather than hard judgments. If an A1C puts you in the prediabetes band, you can use that feedback to experiment with meal timing, movement, and sleep. If you are already being treated for diabetes, the range helps you and your clinician check whether the combination of medication, nutrition, and daily routine is heading where you want. The calculator’s instant conversion to eAG makes it simpler to set goals you can measure against in your routine.

Keep in mind that A1C is one piece of the puzzle. Clinicians often look at fasting glucose, post‑meal values, CGM time‑in‑range, blood pressure, cholesterol, weight, and kidney function to round out the picture. This is where tools like our insulin calculator, adult BMI calculator, and kidney function calculator can give you additional context to discuss with your healthcare team.

Converting mg/dL and mmol/L

Glucose units vary by region. In the U.S., mg/dL is standard; in Canada, the U.K., and much of Europe, mmol/L is common. The conversion is simple: 1 mmol/L ≈ 18 mg/dL. Our calculator shows both values at once so you can compare your lab report with readings from a meter or a companion tool like the blood sugar calculator. That also makes it straightforward to work with international research or guidance that uses different units.

If your meter or app summarizes an average in mmol/L but your lab report uses mg/dL, tap the unit toggle before entering your value. The result appears in both units along with the estimated A1C. Small details like consistent units avoid confusion and help you and your clinician speak the same language when you review progress.

If you’re tracking carbs and adjusting doses, being fluent in unit conversions can reduce friction. Nutrition‑focused tools — for example, the carb calculator and calorie intake calculator — can help align dietary targets with glucose outcomes over time.

A1C vs. daily readings and CGM

Many people notice that A1C doesn’t line up perfectly with what they see day to day. That’s expected: A1C averages weeks of data, while finger‑sticks or CGM capture specific moments. If you usually check fasting only, you might miss post‑meal spikes that raise the average. Conversely, occasional lows can bring the average down without telling the whole story. CGM “time‑in‑range” (often 70–180 mg/dL unless your clinician sets different thresholds) adds helpful nuance: it shows how much of the day you spend near your target even if the A1C is unchanged.

Consider two scenarios. In the first, fasting values look fine but lunch and dinner produce regular spikes; the A1C ends up higher than you expect from morning checks. In the second, you have a few significant lows each week; the eAG might look good even though the day‑to‑day pattern is choppy and risky. Both cases call for targeted tweaks rather than sweeping changes, and your A1C trend plus eAG help you prioritize where to start.

Use your A1C result to ask practical questions. Are most highs coming after breakfast? Do large dinners push you up overnight? Are weekends different from weekdays? Small changes — meal timing, portion size, hydration, sleep — can influence glucose patterns as much as big shifts. If you’re exploring low‑carb approaches, our keto calculator offers a structured way to estimate macros to discuss with a dietitian.

Setting targets and planning

Targets are personal. A newly diagnosed person without other conditions may work toward an A1C near or below 7%, while others — especially those prone to hypoglycemia — may aim a bit higher to reduce risk. Pregnancy targets are often tighter and require individualized care. Your clinician will consider age, medications, kidney function, cardiovascular risk, and your daily routine.

The calculator gives you a quick way to translate a target A1C into a practical eAG. You can then break that into simple habits: adjust a snack, add a walk after meals, or plan more consistent bedtimes. If weight management is part of your plan, use the calorie calculator to estimate daily energy needs and the maintenance calorie calculator to aim for stability before changing intake.

A simple planning sequence many people like is: pick one or two meals to focus on first; choose a small change you can keep (e.g., more protein at breakfast or a 10‑minute walk after dinner); monitor for two weeks; and review the average again. The numbers in this tool give fast feedback without turning your day into a math problem.

How often to test A1C

A1C changes slowly because it reflects a multi‑month window. Many adults without recent medication changes test about every three months; some may test twice a year when stable. If your treatment plan changes or if you’re troubleshooting high or low patterns, your clinician might check more often until the new routine settles. The point is not to chase the number every week; it’s to use periodic averages to see whether the big picture is trending in the right direction.

Because newer red blood cells weigh A1C more than older ones, improvements in the past month can move the needle more than you might expect. That also means short‑term illness or stress can temporarily nudge the value. Looking at trends quarter‑to‑quarter, plus daily logs, makes the signal clearer.

Ways to lower A1C safely

There is no one‑size‑fits‑all approach, and this is not medical advice. Still, a few patterns are common: people often benefit from consistent meal timing, prioritizing fiber and protein, moving more (especially after meals), sleeping enough, and monitoring stress. Incremental changes add up: 10–15 minutes of walking after dinner, swapping one refined carb for a higher‑fiber option, or planning a balanced snack for times you usually over‑correct low blood sugar can all make a visible difference in the eAG you see in our tool.

If medication is part of your plan, your prescriber will tailor type and dose. Some medicines primarily lower fasting values; others blunt post‑meal spikes. Work with your care team and use objective numbers to guide adjustments. Our blood pressure calculator can help you track another key risk factor that often travels with diabetes.

When weight loss is appropriate, aligning energy intake with activity can support better averages. Tools like the macro calculator or calorie deficit calculator help translate big ideas into practical daily numbers. Share your plan with a registered dietitian or diabetes educator when possible.

Special cases and limitations

A1C depends on red blood cell lifespan and the chemistry of hemoglobin. Anything that shortens or lengthens red cell life, or changes the type of hemoglobin, can shift A1C without reflecting true average glucose. Examples include iron‑deficiency or hemolytic anemia, recent blood loss or transfusion, pregnancy, certain kidney or liver diseases, and hemoglobin variants (like sickle trait). In these situations, clinicians may rely more on glucose logs, fructosamine, or CGM reports. The calculator remains useful, but the result should be read with extra caution and professional guidance.

Another nuance: some CGM and meter systems calculate averages in ways that emphasize different parts of the day, or exclude outliers. That can make two “averages” look slightly different. The key is consistency — if you use the same device and method, your personal trend over time will still guide decisions even if the absolute number differs a little from the lab.

When A1C seems out of sync with your daily readings, first check the basics: meter calibration, testing technique, and whether you’re sampling at representative times of day. If the mismatch persists, bring printouts or screenshots to your next visit. Objective data shortcuts guesswork and helps your team pinpoint what to adjust.

Common questions

Does A1C measure the last three months exactly?

Not exactly. It weighs recent weeks a bit more heavily because newer red blood cells contribute more. That’s why a change in habits today can begin to move your next A1C even before the full three months pass.

Why is my eAG higher than my fasting numbers?

Fasting reflects a single moment. eAG includes post‑meal spikes and overnight patterns, which can push the average above a single morning reading. Consider sampling after meals to see the full picture.

What’s a reasonable starting goal?

Many adults target an A1C near or below 7% unless your clinician sets a different range. People at risk for lows, those with lengthy diabetes duration, or with other conditions may use a higher goal for safety.

Can I estimate A1C from my meter?

Yes — switch the calculator to eAG → A1C, enter your typical average from your meter or app, and you’ll see the estimated A1C. If your meter shows mmol/L, choose that unit in the tool first.

Should I change medication based on this tool?

No. Use the numbers to inform conversations with your clinician. Medication decisions consider your full history, labs, and risks, not just a single calculation.

For broader context and to explore related tools, see our complete calculators index and the Health Monitoring & Labs category. These hubs link to glucose, kidney, weight, and cardiovascular tools that commonly accompany A1C conversations.

If you’re new to the topic, start simple: convert your current A1C to eAG, jot the number down, and compare it with your typical daily readings. Then pick one small experiment for the next two weeks and check how the average shifts. A modest change that sticks beats an aggressive plan that fizzles. Use this page as your hub: the calculator at the top for quick math, the guide here for context, and the related calculators for deeper dives.

Frequently Asked Questions