Tool

A1c → Average Blood Sugar Calculator

Enter your HbA1c percentage to see your estimated average glucose (eAG) — what your blood sugar has averaged over the past 2–3 months.

Your HbA1c (%)

Typical range on lab reports: 4.0%–14.0%

Estimated average glucose (eAG)

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Normal <5.7%Prediabetes 5.7–6.4%Diabetes 6.5%+

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How this calculator works

This tool uses the American Diabetes Association's validated formula from the A1c-Derived Average Glucose (ADAG) study:

eAG (mg/dL) = 28.7 × A1c − 46.7

Because your red blood cells live about 3 months, the sugar attached to them reflects your average blood glucose over that time. That's why A1c is such a powerful long-term measure — it can't be "gamed" by fasting the morning of your test.

A1c	Est. Avg Glucose	Category
5.0%	97 mg/dL	Normal
5.7%	117 mg/dL	Prediabetes
6.5%	140 mg/dL	Diabetes
7.0%	154 mg/dL	Diabetes
8.0%	183 mg/dL	Diabetes
9.0%	212 mg/dL	Diabetes

Medically reviewed by Dr. Elena Marsh, MD — Board-Certified Internal Medicine
Last reviewed: March 2026 · Reviewed for US reference ranges

A1c Calculator — FAQ

How is A1c converted to average blood sugar?+

Using the ADA's official formula: estimated average glucose (eAG) in mg/dL = 28.7 × A1c − 46.7. For example, an A1c of 7.0% equals about 154 mg/dL. This formula comes from the landmark ADAG study.

What is a normal A1c?+

Below 5.7% is normal, 5.7–6.4% is prediabetes, and 6.5% or higher indicates diabetes. Most adults with diabetes aim for an A1c below 7%.

Is estimated average glucose the same as my meter readings?+

Not exactly. eAG is a 24-hour average across day and night, while your glucose meter captures single moments — often before meals. Your eAG will usually look higher than your typical pre-meal readings because it includes post-meal peaks.