How is eAG calculated from A1C?

Estimated Average Glucose (eAG) is calculated using the clinical ADA formula: eAG (mg/dL) = 28.7 × A1C - 46.7. For example, an A1C of 6.0% corresponds to an eAG of roughly 126 mg/dL.

What is considered a normal A1C range for adults?

According to the American Diabetes Association (ADA) and CDC, a normal A1C is below 5.7%. Prediabetes is between 5.7% and 6.4%, and diabetes is diagnosed at 6.5% or higher on two separate tests.

A1C / eAG Calculator

Convert between clinical HbA1c percentage and Estimated Average Glucose (eAG) using the official ADA formula.

Conversion Details

What do you want to calculate?

HbA1c (%)

Desired Output Unit

Enter a value to see your converted A1C / eAG result

Written ByFree USA Calculators Clinical Editorial Team

Medically Reviewed ByDr. Sarah Jenkins, RD, LDNRegistered Dietitian & Clinical Nutritionist

Last Clinically Reviewed: October 2026

Scientific Formula & Calculation Methodology (ADAG (A1C-Derived Average Glucose) Linear Regression Formula (Nathan et al., 2008))

eAG (mg/dL) = 28.7 × HbA1c (%) - 46.7. For SI units (mmol/L): eAG (mmol/L) = [28.7 × HbA1c - 46.7] ÷ 18.01559. Conversely: HbA1c (%) = [eAG (mg/dL) + 46.7] ÷ 28.7. The clinical consensus was established by the landmark A1C-Derived Average Glucose study endorsed by the American Diabetes Association (ADA), European Association for the Study of Diabetes (EASD), and International Diabetes Federation (IDF).

Important Clinical Limitations of HbA1c & Estimated Average Glucose (eAG) Calculator

HbA1c reflects red blood cell (erythrocyte) turnover over their standard ~120-day lifespan. Conditions altering erythrocyte survival (such as hemolytic anemia, sickle cell trait, chronic kidney disease on erythropoietin, or recent blood transfusion) cause spuriously inaccurate A1C results.
eAG represents a weighted mathematical average where the preceding 30 days account for roughly 50% of the glycation value, and days 90–120 contribute only 10%.
A single eAG calculation cannot detect rapid acute glycemic volatility, nocturnal hypoglycemia, or severe postprandial spikes that a continuous glucose monitor (CGM) or fingerstick log would reveal.
Pregnancy accelerates erythrocyte turnover, meaning lower clinical A1C targets apply during gestation.

Peer-Reviewed Literature & Recognized Medical Sources

Translating the A1C Assay Into Estimated Average Glucose ValuesDiabetes Care (American Diabetes Association / Nathan et al.)

Standards of Care in Diabetes—2024: Glycemic Goals and HypoglycemiaAmerican Diabetes Association (ADA)

All About Your A1C: Tests, Diagnosis, and ManagementCenters for Disease Control and Prevention (CDC)

Adheres to strict clinical accuracy standards & evidence-based protocols.

About Us•Editorial Policy•Medical Disclaimer

Quick Guide Summary: Essential HbA1c & eAG Facts

1. Normal A1C

< 5.7% (eAG < 117 mg/dL). Indicates healthy long-term glucose regulation.

2. Prediabetes

5.7% to 6.4% (eAG 117–137 mg/dL). High risk for progression to type 2 diabetes.

3. Diabetes Diagnosis

≥ 6.5% (eAG ≥ 140 mg/dL) on two separate clinical evaluations confirms diabetes.

4. Standard ADA Target

For non-pregnant adults with diabetes, the ADA generally recommends an A1C target < 7.0% (eAG < 154 mg/dL).

Clinical A1C to Estimated Average Glucose (eAG) Matrix

The table below illustrates the linear translation between laboratory HbA1c percentages and daily home blood glucose meter values according to the ADAG formula:

HbA1c (%)	eAG (mg/dL)	eAG (mmol/L)	ADA Clinical Classification
5.0%	97 mg/dL	5.4 mmol/L	Normal Healthy Baseline
5.5%	111 mg/dL	6.2 mmol/L	Normal Healthy Baseline
5.7%	117 mg/dL	6.5 mmol/L	Prediabetes Threshold
6.0%	126 mg/dL	7.0 mmol/L	Prediabetes Range
6.5%	140 mg/dL	7.8 mmol/L	Diabetes Diagnostic Cutoff
7.0%	154 mg/dL	8.6 mmol/L	Standard ADA Treatment Target
8.0%	183 mg/dL	10.2 mmol/L	Elevated Glycemic Risk
10.0%	240 mg/dL	13.3 mmol/L	Severe Hyperglycemia / Review Needed

What Exactly is Glycated Hemoglobin (HbA1c)?

Hemoglobin is the iron-rich protein inside red blood cells responsible for transporting oxygen from your lungs to tissues across the body. When glucose circulates in the bloodstream, a fraction of it naturally binds chemically to hemoglobin without the aid of enzymes—a process called non-enzymatic glycation.

Because human red blood cells survive in circulation for approximately 110 to 120 days before being recycled by the spleen, the percentage of glycated hemoglobin provides an immutable 90 to 120 day rolling record of ambient glycemic exposure. Unlike a fasting fingerstick test, which fluctuates by minute based on anxiety or your last meal, HbA1c cannot be fooled by last-minute dieting.

Frequently Asked Questions About A1C

The A1C test reflects your average blood glucose (sugar) level over the past 2 to 3 months by measuring the percentage of hemoglobin coated with sugar (glycated hemoglobin).