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A1C Calculator

Convert HbA1c to estimated average glucose (mg/dL and mmol/L) and to mmol/mol, or average glucose back to A1C, with the ADA ranges.

Enter your HbA1c result and the calculator shows the estimated average glucose (eAG) it corresponds to, in both mg/dL and mmol/L, along with the IFCC value in mmol/mol used in the UK and much of Europe. You can also go the other way: enter an average glucose from a meter or continuous glucose monitor to see the A1C it matches.

A colour scale shows where the value falls in the American Diabetes Association ranges for normal, prediabetes and diabetes, and a table lists common values. The conversions use the formula from the international A1C-Derived Average Glucose (ADAG) study.

How to use A1C Calculator

  1. Choose what you know: HbA1c in % or mmol/mol, or average glucose in mg/dL or mmol/L.
  2. Enter the value from your report or meter.
  3. Read the A1C, the estimated average glucose and the range.
  4. Use the table to compare with other values.

Features

  • HbA1c % ↔ estimated average glucose
  • mg/dL and mmol/L
  • IFCC mmol/mol conversion
  • ADA ranges: normal, prediabetes, diabetes
  • Reference table from 5% to 12%
  • Runs in your browser; nothing is stored or sent

What A1C measures

Glucose in the blood sticks to haemoglobin in red blood cells. Because red cells live about three months, the share of haemoglobin with glucose attached, HbA1c, reflects the average blood sugar over the past two to three months, with the most recent weeks counting most. Unlike a finger-prick reading, it does not change with a single meal, so it is used both to diagnose diabetes and to check how well it is controlled.

From A1C to average glucose

The ADAG study (Nathan and colleagues, Diabetes Care 2008) compared A1C with frequent glucose measurements in over 500 people and found a straight-line relationship: estimated average glucose in mg/dL = 28.7 × A1C − 46.7, or in mmol/L = 1.59 × A1C − 2.59. The IFCC unit is converted with mmol/mol = (A1C % − 2.15) × 10.929.

A1C %mmol/molAverage glucose mg/dLmmol/L
531975.4
5.7391176.5
6.5481407.8
7531548.5
86418310.1
97521211.7
108624013.3

Normal, prediabetes and diabetes ranges

For non-pregnant adults, the American Diabetes Association uses these A1C cut-offs: below 5.7% (39 mmol/mol) is normal, 5.7% to 6.4% (39 to 47 mmol/mol) is prediabetes, and 6.5% (48 mmol/mol) or higher on two tests is diabetes. Many adults with diabetes aim for an A1C below 7% (53 mmol/mol), but targets are personal: a doctor may suggest a lower goal for a young, healthy person or a higher one for an older person who is at risk of low blood sugar.

When A1C can be misleading

Anything that changes how long red blood cells live changes A1C. Anaemia from iron deficiency can raise it; recent blood loss, transfusions, haemolysis, pregnancy and advanced kidney disease can lower it. Some haemoglobin variants, more common in people of African, Mediterranean or South-East Asian descent, interfere with certain lab methods. A1C also hides swings: two people with the same A1C can have very different highs and lows. If your A1C does not fit your meter readings, tell your doctor.

Lowering A1C

Each 1-point fall in A1C is linked to a lower risk of eye, kidney and nerve problems from diabetes. Regular activity, eating fewer refined carbohydrates and sugary drinks, losing weight if overweight, sleeping well and taking prescribed medicines all help. Because A1C reflects three months, wait about three months after a change before judging its effect on the test.

Frequently asked questions

What average blood sugar is an A1C of 7%?

About 154 mg/dL or 8.5 mmol/L, using the ADAG formula. In IFCC units 7% is 53 mmol/mol.

What A1C is normal?

Below 5.7% (39 mmol/mol). 5.7% to 6.4% is prediabetes and 6.5% or above suggests diabetes, confirmed by a second test.

How do I convert A1C % to mmol/mol?

Subtract 2.15 and multiply by 10.929. For example, (7 − 2.15) × 10.929 ≈ 53 mmol/mol.

Can I calculate A1C from my glucose meter average?

Yes, choose average glucose. The result is an estimate; your lab A1C may differ, especially with few readings.

Why does my lab A1C not match my meter?

Meters and A1C measure different things, and anaemia, kidney disease, pregnancy or haemoglobin variants can affect A1C. Discuss it with your doctor.

Is my data saved?

No. Everything is calculated in your browser.

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