A1c Calculator – Hemoglobin A1c to Average Blood Sugar

Convert your Hemoglobin A1c percentage into estimated average glucose (eAG) using the ADAG regression formula, see where it falls against ADA diagnostic categories, and track the change from a prior reading.

Quick Facts

Formula
eAG (mg/dL) = 28.7 × A1c − 46.7
ADAG study regression (Nathan et al., Diabetes Care 2008); mmol/L uses the standard 18.0182 mg/dL-per-mmol/L conversion.
ADA diagnostic thresholds
Normal <5.7% · Prediabetes 5.7-6.4% · Diabetes ≥6.5%
Based on a single reading; diagnosis usually needs a confirmatory test.

Your Results

Calculated
Estimated average glucose
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In your preferred unit
Average glucose (other unit)
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For cross-reference
A1c category
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ADA diagnostic range
Change vs. previous A1c
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Trend since last test

Ready

Enter your A1c percentage to estimate average glucose and see the ADA category.

About the A1c Calculator

Hemoglobin A1c (HbA1c) reflects the percentage of red blood cell hemoglobin that has glucose attached to it, which builds up in rough proportion to average blood sugar over the roughly 8-12 week lifespan of a red blood cell. Because A1c is reported as a percentage, it can be hard to picture in the same units as a home glucose meter. This calculator converts your A1c percentage into an estimated average glucose (eAG) figure in both mg/dL and mmol/L, using the ADA/ADAG-endorsed regression formula, and shows where the reading falls against the standard diagnostic categories.

The formula it uses

The 2008 ADAG (A1c-Derived Average Glucose) study related thousands of paired A1c and continuous glucose monitoring measurements and produced a simple linear regression: estimated average glucose in mg/dL equals 28.7 times the A1c percentage minus 46.7. For example, an A1c of 7.0% corresponds to an eAG of about 154 mg/dL. The calculator then converts that mg/dL figure to mmol/L by dividing by 18.0182, the standard conversion factor between the two glucose units.

Reading the A1c category

The American Diabetes Association defines three bands from a single A1c test: normal is below 5.7%, prediabetes is 5.7% to 6.4%, and diabetes is 6.5% or higher. These are screening thresholds, not a diagnosis by themselves — a result in the prediabetes or diabetes range is typically confirmed with a repeat test or a second measurement method before any diagnosis is made.

When to consult a professional

This calculator performs arithmetic only; it does not diagnose, does not recommend medication or dosing, and cannot account for conditions that affect A1c accuracy (such as certain anemias, hemoglobin variants, or recent blood loss or transfusion). Discuss any A1c result, and any change from a previous reading, with a healthcare provider who has your full medical history.

Frequently Asked Questions

How does the A1c to average glucose conversion work?
This calculator uses the ADAG (A1c-Derived Average Glucose) regression formula published by Nathan and colleagues in Diabetes Care in 2008: estimated average glucose in mg/dL equals 28.7 times the A1c percentage minus 46.7. The mmol/L figure is then obtained by dividing that mg/dL value by the standard glucose conversion factor of 18.0182.
What A1c percentage counts as normal, prediabetes, or diabetes?
Using the American Diabetes Association's diagnostic thresholds, an A1c below 5.7% is considered normal, 5.7% to 6.4% is the prediabetes range, and 6.5% or higher is in the diabetes range. A single reading is not a diagnosis; clinical diagnosis typically requires a repeat test or a second confirmatory measurement.
Is estimated average glucose the same as a blood glucose meter reading?
No. Estimated average glucose (eAG) is a statistical estimate of your average blood sugar over roughly the prior two to three months, derived from the A1c percentage. It will not match any single fingerstick or continuous glucose monitor reading, which reflect blood sugar at one moment in time.

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