Estimated Average Glucose Calculator

Created by Łucja Zaborowska, MD, PhD candidate
Reviewed by Steven Wooding
Based on research by
Nathan DM, Kuenen J, Borg R, Zheng H, Schoenfeld D, Heine RJ; A1c-Derived Average Glucose Study Group Translating the A1C assay into estimated average glucose values. Diabetes Care (June 2008)
Last updated: Sep 29, 2023

The estimated average glucose calculator converts the value of glycated hemoglobin (HbA1c, A1c) to the average blood sugar level in the past 3 months.

Follow the article below to discover HbA1c normal ranges and find out what is eAG and how we should interpret it.

We'll also cover different methods used in A1c/estimated average glucose calculations and look at ready-made blood sugar conversion charts. 🍭

What is HbA1c?

HbA1c is a shorter form for Glycated hemoglobin or Hemoglobin A1c - this term describes a hemoglobin particle that has bonded with a molecule of sugar. HbA1c is usually written as a percentage (%).

💡 Hemoglobin (Hb) is a protein that transports oxygen - it's probably the most important part of a red blood cell.

So how does it all work? Let's start at the beginning:

Glucose is a simple kind of sugar; the human body uses it as its primary energy source. Glucose circulates in our bloodstream and is "pushed" into the cells when they need more of it — the hormone responsible for this action is called insulin.

Here comes the bad news: when the organism doesn't produce enough insulin, there is no other procedure that could eliminate the glucose from the blood and redirect it inside the cells of the body. As a result, the concentration of sugars, including glucose, rises suddenly. 🍩🍫🍬

If there's a lot of sugar in the bloodstream, there's a greater possibility that some sugar particles will bond to hemoglobin, creating HbA1c. That's why we measure HbA1c to indirectly evaluate the action of insulin — we also use it to check whether the patient is following the proper diet and prescribed treatment.

Finally, we come to the grand finale of this short story — the disease that we described, caused by the lack of insulin, or lack of its proper function, is called diabetes mellitus. This condition is chronic and can be treated either with:

  • Artificial insuline 💉; or
  • Oral medication 💊

What is estimated average glucose (eAG)?

Estimated average glucose, eAG (also called: estimated mean glucose, average glucose level) summarizes the blood glucose level during the past 3 months.

We obtain it by transforming the percentage of HbA1c to the eAG value, given either in mg/dL or mmol/L. (You may transform it using the blood sugar converter.)

Why does the eAG measure exactly 3 past months? 🤔

The estimated average glucose range comes from the HbA1c measurements that estimate the amount of the particular protein located within the red blood cells.

The average lifespan of a red blood cell equals 120 days, which is almost 4 months - but we must remember that not all the blood cells are being born and die at the same time. To receive accurate readings, we need to make sure that most of the cells that we study were alive during the period we'd like to measure - that's why we're confident of 3, not 4 months.

🍌 Hey! You can check the foods that increase your estimated average glucose with our glycemic index calculator or glycemic load calculations.

Normal blood sugar levels charts for HbA1c/eAG blood tests

Healthy individuals:

  1. HbA1c

    • 💚 <5.7% — Normal A1c levels for non-diabetics
    • 🔶 5.7-6.5% — A1c prediabetes level
    • 🔺 ≥ 6.5% — Diabetes
  2. Average blood sugar calculated from the HbA1c

    • <139.85 mg/dL or <7.77 mmol/L — Correct level
    • >139.85 mg/dL or >7.77 mmol/L — Diabetes

Individuals with diabetes

  1. HbA1c

    • <6% — Pregnant women with diabetes.
    • < 6.5% — Excellent result for the general population, a good result for children and adolescents (be careful about hypoglycemic episodes!).
    • <7% — Recommended result for general population.
    • <8% — Good result for people over 80 years old, or with severe comobordities.
    • ≥7% — Too high HbA1c for general population.
  2. Average blood sugar calculated from the HbA1c

    • <154.2 mg/dL or <8.57 mmol/L — Estimated average glucose normal range
    • >154.2 mg/dL or >8.57 mmol/L — High level of glucose

Go one step ahead of the game and calculate your insulin dosage or try the Warsaw method of insulin management. 📊

HbA1c conversion to average glucose — Conversion chart

The conversion charts allow you to turn HbA1c to glucose and blood sugar to A1c without using any calculations.









5.4 (4.2-6.7)

97 (76-120)



7.0 (5.5-8.5)

126 (100-152)



8.6 (6.8-10.3)

154 (123-185)



10.2 (8.1-12.1)

183 (147-217)



11.8 (9.4-13.9)

212 (170-249)



13.4 (10.7-15.7)

240 (193-282)



14.9 (12.0-17.5)

269 (217-314)



16.5 (13.3-19.3)

298 (240-347)



18.1 (15-21)

326 (260-380)



19.7 (16-23)

355 (290-410)



21.3 (17-25)

384 (310-440)



22.9 (19-26)

413 (330-480)



24.5 (20-28)

441 (460-510)



26.1 (21-30)

470 (380-540)



27.7 (23-32)

499 (410-570)

How to calculate estimated average glucose

HbA1c estimated average glucose calculation looks just as follows:

Est Avg Glucose = (28.7 × HbA1c) - 46.7


  • Estimate Average Glucose is given in mg/dL; and
  • HbA1c is given in %.
Łucja Zaborowska, MD, PhD candidate
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