Is estimated average glucose the same as my meter’s average?

Not necessarily. eAG is calculated from your HbA1c using a population regression, while a meter average reflects only the specific moments you happened to test. If you test mostly before meals, your meter average will usually read lower than your eAG, because it misses post-meal peaks. Both can be accurate and still differ.

Why does my lab report HbA1c in mmol/mol instead of a percentage?

mmol/mol is the IFCC unit, used in most countries outside the United States. It measures the same thing on a different scale, and the two convert exactly using the NGSP–IFCC master equation. This calculator shows both so a result is readable wherever you are.

What HbA1c counts as normal?

For screening in non-pregnant adults, the American Diabetes Association treats below 5.7% as within the reference range, 5.7–6.4% as the prediabetes range, and 6.5% or above as the diabetes screening threshold. These are screening ranges rather than diagnoses — a diagnosis is made by a clinician, generally with repeat or corroborating testing.

Metabolic HealthDiabetes & Metabolic HealthBlood Tests

HbA1c to Estimated Average Glucose Calculator

Enter an HbA1c result to see the estimated average glucose (eAG) it corresponds to, in both mg/dL and mmol/L, plus the equivalent IFCC value in mmol/mol. Uses the regression the American Diabetes Association applies when reporting eAG.

Updated September 27, 2026

How we calculate it

eAG (mg/dL) = 28.7 × HbA1c(%) − 46.7

HbA1c measures the percentage of hemoglobin in your red blood cells that has glucose attached to it. Because a red blood cell lives around 8–12 weeks, that percentage reflects average glucose exposure over roughly the preceding two to three months, weighted toward the most recent weeks. This calculator converts an HbA1c percentage into an estimated average glucose using the linear regression published from the A1c-Derived Average Glucose (ADAG) study: eAG in mg/dL equals 28.7 multiplied by HbA1c, minus 46.7. That is the same equation the American Diabetes Association uses to report eAG alongside an HbA1c result. The mmol/L figure is derived by dividing the mg/dL result by 18.0182, the conversion factor that follows from the molar mass of glucose, rather than being calculated from a second equation — so the two outputs can never disagree. The IFCC value in mmol/mol is produced with the NGSP–IFCC master equation, IFCC = (NGSP% − 2.15) × 10.929.

Important limitations

eAG is derived from a population regression line. Your own average glucose can differ meaningfully from the estimate even when the HbA1c measurement itself is accurate.
HbA1c depends on red blood cells, so anemia, recent blood loss or transfusion, pregnancy, chronic kidney disease, hemolysis and erythropoietin treatment can all shift the result independently of your actual glucose.
Certain hemoglobin variants, including HbS, HbC, HbE and HbF, interfere with some HbA1c assays and may require the laboratory to use an alternative method.
HbA1c says nothing about variability. Two people with an identical HbA1c can have very different daily highs and lows, which is clinically important and invisible here.
The screening ranges shown are for non-pregnant adults. Thresholds in pregnancy, in children and in some other groups are different.
An eAG figure is not interchangeable with a fingerstick or continuous-glucose-monitor reading, which measure glucose at a single moment.

Frequently asked questions

Sources

This page is based on the following sources. Each was reviewed on the access date shown.

Translating the A1C assay into estimated average glucose values(opens in a new tab)
Diabetes Care (American Diabetes Association)
Peer-reviewed articlePublished August 1, 2008Accessed September 27, 2026DOI 10.2337/dc08-0545
Understanding A1C(opens in a new tab)
American Diabetes Association
Professional societyAccessed September 27, 2026
The A1C Test and Diabetes(opens in a new tab)
National Institute of Diabetes and Digestive and Kidney Diseases (NIH)
Government health agencyAccessed September 27, 2026
HbA1c standardization and the NGSP–IFCC master equation(opens in a new tab)
National Glycohemoglobin Standardization Program
Reference workAccessed September 27, 2026
Diagnosis and Classification of Diabetes: Standards of Care in Diabetes-2026(opens in a new tab)
Diabetes Care (American Diabetes Association)
Clinical guidelinePublished January 1, 2026Accessed October 1, 2026

Medical disclaimer. Gravis Labs provides general educational information and calculation tools. Results may be estimates and are not a medical diagnosis or a substitute for professional medical advice, clinical examination, clinical judgment, or treatment.

In an emergency. Do not use Gravis Labs for medical emergencies. If you believe you are experiencing a medical emergency, contact your local emergency services or seek urgent medical care.

Scope. Gravis Labs is an information and calculation service. It is not a medical device, and it is not registered, approved, certified or cleared by any medical regulator or health authority. Nothing here carries clinical authority: every result is an estimate produced by a published equation, and anything that matters for your health needs the opinion of a qualified clinician who can examine you and see your full history.

Read the full medical disclaimer.

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