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How to Use the A1C Calculator — Convert A1C to eAG in mg/dL & mmol/L
1. Select your conversion mode
Choose whether you want to convert A1C to eAG or eAG to A1C using the toggle tabs at the top of the calculator. "A1C → eAG" mode accepts your hemoglobin A1C percentage and returns your estimated average glucose in both mg/dL and mmol/L. "eAG → A1C" mode accepts an average glucose value in either unit and returns the equivalent A1C percentage — useful if you have home glucose readings and want to estimate your A1C.
2. Enter your value
In A1C mode, enter your most recent A1C percentage — typically between 4% and 13%. In eAG mode, enter your estimated average glucose in mg/dL (roughly 70 to 350 for most people with diabetes) or in mmol/L (roughly 4 to 19). The A1C conversion calculator updates your results in real time as you type — no button click needed. If you enter a value in mmol/L, the mg/dL field syncs automatically, and vice versa.
3. Review your results and risk category
The calculator instantly displays three result cards showing your A1C percentage, eAG in mg/dL, and eAG in mmol/L. Below the cards, a color-coded risk badge appears: Green for Normal (A1C below 5.7%), Amber for Prediabetes (A1C 5.7% to 6.4%), or Red for Diabetes (A1C 6.5% and above). This classification follows the American Diabetes Association guidelines and gives you a quick visual summary of where your glucose control stands.
4. Use the reference table for context
Scroll down to see the full A1C reference table showing values from 5% to 13% alongside their eAG equivalents in both mg/dL and mmol/L. Each row is color-coded by risk category so you can see at a glance how different A1C levels map to average glucose and diabetes risk. The row closest to your current result is highlighted automatically, making it easy to see where you sit relative to other A1C values.
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A1C Calculator — Convert A1C to eAG in mg/dL & mmol/L Formulas
A1C to eAG (mg/dL)
eAG (mg/dL) = (28.7 × A1C%) − 46.7
This is the primary A1C to eAG conversion formula endorsed by the American Diabetes Association. It is based on clinical studies that correlated A1C values with actual measured average daily blood glucose. For example: an A1C of 7% converts to (28.7 × 7) − 46.7 = 154.2 mg/dL. The formula is linear and reliable across the full range of typical A1C values from 5% to 13%.
eAG (mg/dL) to mmol/L
eAG (mmol/L) = eAG (mg/dL) ÷ 18.0182
This is the standard unit conversion used worldwide to convert mg/dL to mmol/L. The divisor 18.0182 is the molecular weight of glucose. Using the example above: 154.2 mg/dL ÷ 18.0182 = 8.56 mmol/L. The conversion is exact and bidirectional — multiplying mmol/L by 18.0182 converts back to mg/dL. This calculator handles both directions automatically.
eAG (mg/dL) to A1C
A1C% = (eAG (mg/dL) + 46.7) ÷ 28.7
This is the reverse formula, rearranged from the primary A1C to eAG equation. It allows you to calculate A1C from an average blood glucose reading. For example: if your eAG is 155 mg/dL, then (155 + 46.7) ÷ 28.7 = 7.02%, or approximately 7%. This is useful when you have home glucose meter data and want to estimate what your A1C might look like at your next lab test.
eAG (mmol/L) to mg/dL
eAG (mg/dL) = eAG (mmol/L) × 18.0182
The reverse of the mmol/L conversion formula. If you have a glucose reading in mmol/L and need it in mg/dL, multiply by 18.0182. For example: 8.5 mmol/L × 18.0182 = 153.2 mg/dL. This is the standard conversion used in clinical practice. This A1C calculator handles this conversion automatically when you enter a value in the mmol/L field.
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Key Factors
A1C test accuracy and limitations
A1C is a reliable indicator of average glucose control, but certain medical conditions can cause inaccurate results. Hemolytic anemia, polycythemia vera, kidney disease, liver disease, pregnancy, and abnormal hemoglobin variants can all produce misleading A1C readings. If your A1C seems inconsistent with your daily home glucose readings, ask your doctor about alternative tests such as fructosamine (which reflects glucose over 2 to 3 weeks) or a continuous glucose monitor for a more accurate picture.
Individual variation in the A1C to eAG relationship
The conversion formula used in this A1C calculator is based on large clinical studies and represents an average relationship across populations. However, individual glucose patterns vary widely. Two people with the same A1C might have very different daily glucose profiles — one person may have stable readings around 140 mg/dL all day, while another swings between 70 and 220 mg/dL. Both could have identical A1C results. For this reason, eAG should be viewed as an estimate of your average, not an exact daily value.
Tracking both A1C and daily glucose readings
A1C captures long-term control but misses day-to-day variability that matters for medication adjustments and hypoglycemia risk. Home glucose testing — whether fingerstick readings or a continuous glucose monitor — shows real-time patterns and helps identify when highs and lows occur throughout the day. Together, A1C and daily readings provide a complete picture of your diabetes management. Use this hemoglobin A1C calculator to connect your home glucose data to your long-term A1C trend.
Time lag in A1C changes
Because A1C reflects your average glucose over 2 to 3 months, changes in your diabetes management do not appear in A1C results immediately. Starting a new medication or making a significant lifestyle change typically takes 8 to 12 weeks to meaningfully move your A1C. In the interim, daily home glucose readings let you see whether your new approach is working before waiting months for your next lab result. Use this online A1C calculator regularly to track your estimated progress between lab tests.
Variability between laboratories and test methods
Different labs may use slightly different A1C measurement methods, and results can vary by approximately ±0.2% depending on the lab and testing equipment. For this reason, it is best to have your A1C tested at the same lab when tracking progress over time. If you switch healthcare providers or labs, ask whether the new lab's A1C results are directly comparable to your previous lab's reports.
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Sizing Guide
Normal glucose control
A1C below 5.7%
A1C values below 5.7% indicate normal fasting glucose with no diabetes or prediabetes. This is the target range for people without diabetes. Maintaining this level through regular physical activity, a diet rich in whole foods, and a healthy body weight significantly reduces the risk of developing type 2 diabetes. Use this A1C calculator periodically to monitor your estimated eAG and stay aware of any upward trends.
Prediabetes range
A1C 5.7% to 6.4%
Prediabetes is a warning that blood glucose is rising and diabetes risk is elevated. The encouraging news is that prediabetes can often be reversed through lifestyle changes: regular physical activity (at least 150 minutes per week), modest weight loss of 5 to 10%, and a diet emphasizing vegetables, whole grains, and lean proteins. Many people in the prediabetes range successfully lower their A1C back to normal with consistent effort over 3 to 6 months.
Diabetes diagnosis
A1C 6.5% and above
An A1C of 6.5% or above confirms a diabetes diagnosis when backed by a lab test. Most people with diabetes can achieve meaningful glucose control with the right combination of medication, dietary changes, physical activity, and regular A1C monitoring. Your healthcare provider will help you set a personal A1C target — commonly 7% or below — and develop a treatment plan tailored to your health history and lifestyle.
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Frequently Asked Questions
Disclaimer
This free A1C calculator provides an estimated average glucose based on the standard ADA conversion formula (eAG = 28.7 × A1C% − 46.7). It is intended for educational and informational purposes only and does not constitute medical advice, diagnosis, or treatment. A1C results can vary based on individual biology, lab methods, and certain medical conditions. Always consult your healthcare provider for interpretation of your actual A1C lab results and for guidance on diabetes prevention or management.
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