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Glucose to A1C Calculator

mg/dL

Your Results

An average glucose of 126 mg/dL (7.0 mmol/L) matches an estimated A1C of 6.0%, or 42 mmol/mol, which is in the prediabetes range on the usual scale. A CGM's Glucose Management Indicator for the same average would be 6.3%. It's an estimate: a lab A1C test can differ by half a point or more, and only a doctor can diagnose diabetes.

6.0%
Estimated A1C
Prediabetes
Range
42 mmol/mol
IFCC Units
7.0
Average in mmol/L
6.3%
CGM Estimate (GMI)

Where your A1C falls on the usual scale

  • Normal, under 5.7%
  • Prediabetes, 5.7% to 6.4%
  • Diabetes, 6.5% and up
Glucose to A1C Chart
A1Cmg/dLmmol/Lmmol/molRange
5.0%975.431Normal
5.5%1116.237Normal
5.7%1176.539Prediabetes
6.0%1267.042Prediabetes
6.5%1407.848Diabetes
7.0%1548.653Diabetes
7.5%1699.458Diabetes
8.0%18310.264Diabetes
8.5%19710.969Diabetes
9.0%21211.775Diabetes
9.5%22612.580Diabetes
10.0%24013.386Diabetes
11.0%26914.997Diabetes
12.0%29816.5108Diabetes

Average glucose for each A1C by the ADA formula: glucose = 28.7 × A1C − 46.7. Your result is highlighted. Ranges are the American Diabetes Association's.

What Is A1C?

A1C, also called HbA1c or hemoglobin A1c, is a blood test that shows your average blood sugar over the past two to three months. Sugar in the blood sticks to hemoglobin in red blood cells, and those cells live about three months, so the share that's coated tracks your long-term average. The higher your average glucose, the higher your A1C.

  • Under 5.7%: the normal range.
  • 5.7% to 6.4%: the prediabetes range, a higher risk of type 2 diabetes.
  • 6.5% or higher: the diabetes range. A doctor confirms a diagnosis with a lab test, usually repeated.
  • Estimated average glucose (eAG): the same information as A1C, but in mg/dL or mmol/L like a meter reading.

This calculator works backwards: from an average blood sugar to the A1C it usually goes with. It's useful between lab tests, but it's an estimate, not a test result.

Which calculator should I use?

  • Glucose to A1C Calculator: to estimate your A1C from the average on your meter or CGM.
  • HOMA-IR Calculator: to estimate insulin resistance from a fasting glucose and insulin test.
  • Calorie Calculator: to see how many calories you need in a day.
  • Steps to Miles Calculator: to turn a day's steps into distance and calories burned.

How to Calculate A1C From Glucose

The American Diabetes Association uses the formula from the A1C-Derived Average Glucose (ADAG) study, turned around:

A1C= glucose+46.728.7

For a continuous glucose monitor, the Glucose Management Indicator (GMI) is the better match:

GMI=3.31+0.02392×glucose
  • Glucose: your average blood sugar in mg/dL over two to three months. For mmol/L, multiply by 18.016 first.
  • A1C and GMI: in percent. For the international unit, mmol/mol = (A1C − 2.15) × 10.929.

Example

An average meter reading of 126 mg/dL:

  • A1C: (126 + 46.7) ÷ 28.7 = 6.02%, about 6.0%, in the prediabetes range.
  • In mmol/mol: (6.02 − 2.15) × 10.929 = 42.
  • In mmol/L, the same average is 126 ÷ 18.016 = 7.0 mmol/L.
  • From a CGM, the GMI would be 3.31 + 0.02392 × 126 = 6.32%.

How to Use the Glucose to A1C Calculator

"My meter says my 90-day average is 126 mg/dL. What A1C does that point to, and which range is it in?" This calculator answers that.

Let's enter the numbers for this example in each box. They are already filled in when the calculator opens, so you can follow along and then change any box to match your own readings.

  • Glucose Unit: Choose mg/dL (US). mmol/L is used in the UK, Canada, Australia and many other countries. Switching converts the number you've typed.
  • Average Glucose: Enter 126, your average blood sugar over the last two to three months. From 40 to 600 mg/dL, or 2.2 to 33.3 mmol/L. The up and down arrows beside the box, or the arrow keys, change it by 1 mg/dL (0.1 mmol/L) and update the results right away.
  • Glucose From: Choose Meter or lab average. Choose CGM average if the number comes from a continuous glucose monitor.

Calculate and Reset

Click Calculate to see your results. If the glucose box has a problem, such as letters or a number out of range, a message pops up under it instead. With the default numbers you get:

  • Your Results: a short summary in words: an estimated A1C of 6.0%, its range, and the CGM estimate for comparison.
  • Estimated A1C: the headline, 6.0%.
  • Range: Prediabetes, on the American Diabetes Association's scale.
  • IFCC Units: 42 mmol/mol, the unit many labs outside the US report.
  • Average in mmol/L: 7.0, the same glucose in the other unit.
  • CGM Estimate (GMI): 6.3%, what the other formula gives, to show how much they can differ.
  • Where your A1C falls on the usual scale: a bar split into the normal, prediabetes and diabetes ranges, with a marker at yours.
  • Glucose to A1C Chart: the average glucose for A1C from 5% to 12%, in mg/dL, mmol/L and mmol/mol, with yours highlighted.
  • Share Results: a link that opens this calculator with your numbers filled in. Copy it, or share it on Facebook or X.

Click Reset to put every box back to its default. A lab A1C can differ from this estimate by half a point or more, and anemia, some hemoglobin types, pregnancy and kidney disease can make A1C and glucose disagree. This is for information only, not medical advice: talk to your doctor about your results.