Free tool

A1c to Estimated Average Glucose (eAG) Calculator

Q: Why does my meter average not match the eAG?

eAG is a population regression from the ADAG study, and glycation rates differ between people, so true mean glucose at a given A1c varies by 20–30 mg/dL either way. Meter averages also skew toward the times you test (often fasting), which are lower than the all-day mean.

Q: What A1c is normal, prediabetes and diabetes?

The American Diabetes Association uses under 5.7% as normal, 5.7–6.4% as prediabetes and 6.5% or higher as the laboratory criterion for diabetes, confirmed on a second test. For most adults with diabetes the treatment target is under 7%, an eAG of about 154 mg/dL.

Q: When is A1c unreliable?

Anything that changes red-cell lifespan or hemoglobin: iron-deficiency or hemolytic anemia, hemoglobin variants such as HbS or HbC, recent transfusion, pregnancy, advanced kidney disease and some HIV medications. In those situations fasting glucose or a fructosamine test is used instead.

The short answer

Enter a hemoglobin A1c in percent or mmol/mol and the calculator returns the estimated average glucose (eAG) in mg/dL and mmol/L using the ADAG study equation, 28.7 × A1c − 46.7. It also places the A1c in the American Diabetes Association categories: under 5.7% normal, 5.7–6.4% prediabetes, 6.5% and above diabetes when confirmed.

Input: A1c % or mmol/mol
Equation: ADAG (Nathan 2008)
Outputs: mg/dL · mmol/L
Cost: Free

Hemoglobin A1c

NGSP % (US) or IFCC mmol/mol · Hemoglobin A1c range

Enter your values to calculate.

eAG [mg/dL] = 28.7 × A1c[%] − 46.7 · eAG [mmol/L] = 1.59 × A1c[%] − 2.59 (ADAG study)

Educational — a derived index, not a diagnosis. Nothing you enter leaves your browser.

How the Estimated average glucose is calculated

eAG [mg/dL] = 28.7 × A1c[%] − 46.7 · eAG [mmol/L] = 1.59 × A1c[%] − 2.59 (ADAG study)

Worked example

Hemoglobin A1c (%)	Estimated average glucose (mg/dL)
5.6	114

eAG (SI): 6.3 mmol/L · A1c: 5.6% · 38 mmol/mol

Falls in: A1c below 5.7% — normal range.

How to read the result

Estimated average glucose	Reads as	What it usually means
< 117	A1c below 5.7% — normal range	An A1c under 5.7% (eAG below about 117 mg/dL) is the American Diabetes Association's normal range. The eAG is the average glucose your red cells were exposed to over roughly the past three months.
117 – 140	A1c 5.7–6.4% — prediabetes range	A1c 5.7–6.4% corresponds to an eAG of about 117–139 mg/dL and is the ADA's prediabetes range. The ADA recommends confirming with a repeat test and addressing weight, activity and diet.
≥ 140	A1c 6.5% and above — diabetes range	A1c of 6.5% or higher (eAG about 140 mg/dL and above) meets the ADA laboratory criterion for diabetes when confirmed on a second test. In treated diabetes, an A1c under 7% (eAG ≈ 154 mg/dL) is the general target for most adults.

Cut points reviewed by Youmna DiStefano, MD on 2026-09-26. Sources below.

Limits

eAG is a population regression, not your meter average: two people with the same A1c can differ by 20–30 mg/dL in true mean glucose. Anemia, hemoglobin variants, recent transfusion, pregnancy and kidney disease make A1c (and therefore eAG) unreliable, and the ADA categories require confirmation on a second test.

Sources

Nathan DM, et al. Translating the A1C assay into estimated average glucose values. Diabetes Care 2008;31:1473–1478. doi.org/10.2337/dc08-0545
American Diabetes Association. 2. Diagnosis and Classification of Diabetes: Standards of Care in Diabetes—2025. Diabetes Care 2025;48(Suppl 1):S27–S49. doi.org/10.2337/dc25-S002
NGSP. IFCC and NGSP A1c standardization; master equation. ngsp.org/ifcc.asp

Frequently asked questions

Why does my meter average not match the eAG?

eAG is a population regression from the ADAG study, and glycation rates differ between people, so true mean glucose at a given A1c varies by 20–30 mg/dL either way. Meter averages also skew toward the times you test (often fasting), which are lower than the all-day mean.

What A1c is normal, prediabetes and diabetes?

The American Diabetes Association uses under 5.7% as normal, 5.7–6.4% as prediabetes and 6.5% or higher as the laboratory criterion for diabetes, confirmed on a second test. For most adults with diabetes the treatment target is under 7%, an eAG of about 154 mg/dL.

When is A1c unreliable?

Anything that changes red-cell lifespan or hemoglobin: iron-deficiency or hemolytic anemia, hemoglobin variants such as HbS or HbC, recent transfusion, pregnancy, advanced kidney disease and some HIV medications. In those situations fasting glucose or a fructosamine test is used instead.

Which biomarkers does this tool cover?

Which tests give you these numbers?

Physician-authorized, drawn at Quest, Labcorp or BioReference. Results in 1–3 business days for most tests.