Convert your HbA1c percentage into estimated average glucose (eAG) using the ADAG equation.
📖 ADAG Study EquationFill in the fields on the left with your information, then press Calculate to see your result instantly. No sign-up required, and no data is sent anywhere — everything is calculated right in your browser.
The HbA1c (glycated hemoglobin) test measures the percentage of hemoglobin proteins in your red blood cells that have glucose attached to them. Because red blood cells live for roughly three months, HbA1c reflects your average blood sugar level over that entire period rather than a single moment, which is what makes it one of the most reliable tests for diagnosing and monitoring diabetes. This calculator converts an HbA1c percentage into an estimated average glucose (eAG) reading using the equation derived from the ADAG (A1c-Derived Average Glucose) study, an international study published in Diabetes Care (Nathan et al., 2008) that linked HbA1c values to real glucose readings collected through continuous monitoring in hundreds of participants. The eAG result is shown in both mg/dL and mmol/L so it can be compared directly with the numbers on a home glucose meter. Per American Diabetes Association (ADA) criteria, an HbA1c below 5.7% is considered normal, 5.7%–6.4% falls in the prediabetes range, and 6.5% or higher is consistent with diabetes. This tool is for educational purposes only and does not replace a laboratory test or a physician's diagnosis.
Lab reports usually hand back an HbA1c result as a single percentage, and for most people that number means very little on its own. Estimated Average Glucose (eAG) exists to bridge that gap: it restates the same lab result in the mg/dL or mmol/L units that appear every day on a home glucose meter, so a person managing diabetes can see how their three-month average compares with their daily finger-stick readings instead of mentally translating between two unrelated scales.
The conversion is not a guess. It comes from the ADAG (A1c-Derived Average Glucose) study, a multi-center international project that fitted continuous glucose monitors to several hundred participants for months at a time and compared the resulting glucose averages against each person's lab-measured HbA1c. That data produced the now-standard linear relationship — eAG (mg/dL) = 28.7 × HbA1c − 46.7 — which this calculator applies directly, along with the mmol/L conversion (dividing by 18) used in most countries outside the United States.
Clinically, the result is usually read against three bands set by the American Diabetes Association: below 5.7% (normal), 5.7% to 6.4% (prediabetes), and 6.5% or above (diabetes range, typically confirmed with a repeat test or a second diagnostic method). Because HbA1c reflects the roughly 120-day lifespan of a red blood cell, it smooths out day-to-day spikes and dips that a single glucose reading would catch, which is exactly why physicians rely on it for long-term monitoring rather than daily management decisions.
There are limits worth knowing. Conditions that shorten or alter red blood cell survival — such as anemia, certain hemoglobin variants, chronic kidney disease, or pregnancy — can distort the relationship between HbA1c and true average glucose, sometimes making the lab value read higher or lower than a person's actual glucose exposure. For that reason, HbA1c and eAG are best used alongside home glucose logs rather than in isolation, and any unexpected result should be discussed with a physician rather than self-interpreted.
Most people with diagnosed diabetes have HbA1c checked two to four times a year, depending on how stable their control is, while people without diabetes typically only see the number once during a routine screening. Either way, this calculator's role is narrow and specific: it translates a percentage you already have into a glucose-equivalent number that is easier to reason about — it does not measure, diagnose, or replace the blood draw itself.
An HbA1c below 5.7% is generally considered normal, 5.7%–6.4% suggests prediabetes, and 6.5% or higher suggests diabetes.
eAG (estimated Average Glucose) translates the HbA1c percentage into a glucose number in the same units as a home glucose meter, making it easier to relate to daily readings.
No. This calculator only converts an existing HbA1c value; it cannot measure or diagnose your blood sugar level.