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Average Blood Sugar (A1C) Calculator

Convert an A1C percentage into estimated average glucose (eAG) in mg/dL and mmol/L using the ADA formula.

The ADA formula converts A1C to estimated average glucose: eAG (mg/dL) = 28.7 × A1C − 46.7. An A1C of 7% gives an eAG of about 154 mg/dL (8.6 mmol/L). This estimates average glucose from a known A1C result; it does not diagnose diabetes on its own.

Formula Verified by Dr. Sarah Jenkins, PhD

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Saved Runs

Inputs

A1C (%)

Results

Estimated Average Glucose (eAG)

154 mg/dL

eAG in mmol/L8.6

A1C Reference CategoryDiabetes range

Tip

Save this page to translate each new A1C lab result into the mg/dL or mmol/L numbers you're used to seeing on a glucose meter.

Formula

ADA eAG formula

eAG (mg/dL) = 28.7 × A1C − 46.7. eAG (mmol/L) = eAG (mg/dL) ÷ 18.0182.

The American Diabetes Association formula from the ADAG study, also used by the EASD and IDF.

Step by step

How the calculation works

1Enter an A1C percentage from a lab result you already have.
2Review the estimated average glucose in both mg/dL and mmol/L.
3Compare against your typical glucose meter readings as a rough sanity check.
4Discuss any diagnosis, category, or treatment questions with a healthcare provider — this tool converts a known A1C, it does not screen for diabetes.

Example

Worked example: A1C of 7%

eAG = 28.7 × 7 − 46.7 = 154.2 mg/dL, which converts to about 8.6 mmol/L — the same example the ADA itself commonly cites.

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Average Blood Sugar (A1C) Calculator

Convert an A1C percentage into estimated average glucose (eAG) in mg/dL and mmol/L using the ADA formula.

Formula Verified by Dr. Sarah Jenkins, PhD

How to understand and use this calculator

What A1C actually measures

A1C (also called HbA1c or glycated hemoglobin) measures the percentage of hemoglobin in red blood cells that has glucose attached to it. Because red blood cells live for roughly 2-3 months, A1C reflects an average of blood glucose exposure over that window, not a single moment in time the way a finger-stick or continuous glucose monitor reading does. That's exactly what makes it useful for tracking overall control, and exactly why it can be hard to intuitively relate to the day-to-day mg/dL or mmol/L numbers a glucose meter shows.

The real ADA formula, not an approximation

The American Diabetes Association, based on the ADAG (A1C-Derived Average Glucose) study, established the formula: eAG (mg/dL) = 28.7 × A1C − 46.7. This same formula is used by the ADA, EASD, and IDF. To convert the result to mmol/L (the unit used in much of the world outside the US), divide the mg/dL result by 18.0182. This calculator uses that exact formula rather than a rounded or simplified version, so the eAG value it shows matches what the ADA's own conversion tool would return for the same A1C input.

Why eAG is useful alongside daily glucose readings

A1C alone is reported as a percentage, which doesn't map intuitively onto the mg/dL or mmol/L scale most people see on a glucose meter dozens of times a week. eAG translates the lab result into that familiar scale, making it easier to sanity-check: if your meter typically reads somewhere in the 140s mg/dL, an eAG in that same range from your latest A1C is a rough confirmation the two data sources agree, while a large mismatch is worth discussing with a clinician.

A1C diagnostic categories, for context only

The ADA's standard A1C categories are: below 5.7% considered normal, 5.7%-6.4% considered prediabetes range, and 6.5% or above meeting the threshold used for a diabetes diagnosis (typically confirmed with a repeat test or additional criteria). This calculator is built for people who already have an A1C number and want to understand it in glucose terms — it converts a known A1C into eAG, it does not screen for or diagnose diabetes on its own, and a single A1C value should always be interpreted by a clinician alongside symptoms, other labs, and repeat testing where appropriate.

Worked example: an A1C in the diabetes-treatment range

An A1C of 7%: eAG = 28.7 × 7 − 46.7 = 200.9 − 46.7 = 154.2 mg/dL, which converts to 154.2 ÷ 18.0182 ≈ 8.6 mmol/L. This is the same example the ADA itself commonly cites, confirming the formula implementation here matches the published conversion.

Worked example: a higher A1C

An A1C of 9%: eAG = 28.7 × 9 − 46.7 = 258.3 − 46.7 = 211.6 mg/dL, which converts to 211.6 ÷ 18.0182 ≈ 11.7 mmol/L — illustrating how a 2-percentage-point A1C difference (7% to 9%) corresponds to roughly a 57 mg/dL difference in estimated average glucose.

Limitations worth knowing

eAG is an average — it cannot show daily highs, lows, meal spikes, or your current glucose level the way a meter or continuous glucose monitor can. A1C (and therefore any eAG derived from it) can also be thrown off by anything that changes red blood cell lifespan, including certain anemias, kidney disease, recent blood transfusion, and pregnancy — in those situations, A1C may not reflect glucose control as accurately as it normally would, and other monitoring methods matter more.

Related concepts

A1C (HbA1c)

The percentage of hemoglobin with glucose attached, reflecting average blood glucose over roughly the past 2-3 months.

eAG (Estimated Average Glucose)

An A1C result converted into the mg/dL or mmol/L scale used by glucose meters, via the ADA formula eAG = 28.7 × A1C − 46.7.

ADAG study

The A1C-Derived Average Glucose study that established the relationship between A1C and average glucose used by the ADA, EASD, and IDF.

Frequently Asked Questions

What is the A1C to eAG formula?+

eAG (mg/dL) = 28.7 × A1C − 46.7. This is the American Diabetes Association's formula from the ADAG study, also used by the EASD and IDF. Divide by 18.0182 to convert the result to mmol/L.

What does an A1C of 7% mean in average blood sugar?+

About 154 mg/dL (8.6 mmol/L), using the ADA's eAG formula: 28.7 × 7 − 46.7 = 154.2 mg/dL.

Does this calculator diagnose diabetes?+

No. It converts an A1C percentage you already have into an estimated average glucose. Diagnosis requires clinical evaluation, typically including repeat testing, and should always involve a healthcare provider.

What A1C level indicates diabetes?+

The ADA's standard threshold is 6.5% or higher, typically confirmed with a repeat test. 5.7%-6.4% is the prediabetes range, and below 5.7% is considered normal — these are diagnostic reference categories, not something this calculator determines from an eAG conversion alone.

Why doesn't my eAG match what my glucose meter shows day to day?+

eAG is a 2-3 month average derived from A1C, while a meter shows a single moment. Day-to-day readings naturally vary above and below the average — a mismatch isn't necessarily an error, but a persistent large gap is worth discussing with a clinician.

Can conditions other than diabetes affect A1C accuracy?+

Yes. Anything that changes red blood cell lifespan — certain anemias, kidney disease, recent blood transfusion, and pregnancy among them — can make A1C (and any eAG derived from it) less reliable as a glucose-control indicator.

Is mg/dL or mmol/L the right unit for me?+

The US commonly uses mg/dL; most other countries use mmol/L. This calculator shows both, so use whichever matches your glucose meter or the units your clinician's records use.

How the calculation works

1Enter an A1C percentage from a lab result you already have.

2Review the estimated average glucose in both mg/dL and mmol/L.

3Compare against your typical glucose meter readings as a rough sanity check.

4Discuss any diagnosis, category, or treatment questions with a healthcare provider — this tool converts a known A1C, it does not screen for diabetes.

How to understand and use this calculator

What A1C actually measures

The real ADA formula, not an approximation

Why eAG is useful alongside daily glucose readings

A1C diagnostic categories, for context only

Worked example: an A1C in the diabetes-treatment range

Worked example: a higher A1C

Limitations worth knowing

Related concepts

A1C (HbA1c)

The percentage of hemoglobin with glucose attached, reflecting average blood glucose over roughly the past 2-3 months.

eAG (Estimated Average Glucose)

An A1C result converted into the mg/dL or mmol/L scale used by glucose meters, via the ADA formula eAG = 28.7 × A1C − 46.7.

ADAG study

The A1C-Derived Average Glucose study that established the relationship between A1C and average glucose used by the ADA, EASD, and IDF.

Frequently Asked Questions

What is the A1C to eAG formula?+

eAG (mg/dL) = 28.7 × A1C − 46.7. This is the American Diabetes Association's formula from the ADAG study, also used by the EASD and IDF. Divide by 18.0182 to convert the result to mmol/L.

What does an A1C of 7% mean in average blood sugar?+

About 154 mg/dL (8.6 mmol/L), using the ADA's eAG formula: 28.7 × 7 − 46.7 = 154.2 mg/dL.

Does this calculator diagnose diabetes?+

What A1C level indicates diabetes?+

Why doesn't my eAG match what my glucose meter shows day to day?+

Can conditions other than diabetes affect A1C accuracy?+

Is mg/dL or mmol/L the right unit for me?+

The US commonly uses mg/dL; most other countries use mmol/L. This calculator shows both, so use whichever matches your glucose meter or the units your clinician's records use.

Average Blood Sugar (A1C) Calculator

Inputs

Results

ADA eAG formula

How the calculation works

Worked example: A1C of 7%

Learn more about this calculation

How to Use Do The Calculation Calculators: A Practical Step-by-Step Guide

Understanding Calculator Formulas: How DTC Turns Inputs into Results

Average Blood Sugar (A1C) Calculator

Inputs

Results

Key output metrics

How to understand and use this calculator

What A1C actually measures

The real ADA formula, not an approximation

Why eAG is useful alongside daily glucose readings

A1C diagnostic categories, for context only

Worked example: an A1C in the diabetes-treatment range

Worked example: a higher A1C

Limitations worth knowing

Related concepts

Frequently Asked Questions

ADA eAG formula

How the calculation works

Worked example: A1C of 7%

Learn more about this calculation

How to Use Do The Calculation Calculators: A Practical Step-by-Step Guide

Understanding Calculator Formulas: How DTC Turns Inputs into Results

Key output metrics

How to understand and use this calculator

What A1C actually measures

The real ADA formula, not an approximation

Why eAG is useful alongside daily glucose readings

A1C diagnostic categories, for context only

Worked example: an A1C in the diabetes-treatment range

Worked example: a higher A1C

Limitations worth knowing

Related concepts

Frequently Asked Questions