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A1C Calculator

Turn an A1C result into estimated average glucose in mg/dL and mmol/L, or turn an average glucose into the matching A1C.

Level: Grade 9

Printable worksheet

A1C Calculator

Inputs
I know my

Result

Estimated average glucose (eAG)

126 mg/dL

An A1C of 6 % matches an estimated average glucose of about 126 mg/dL (7 mmol/L) on the ADAG formula. Talk with your doctor about what your own results mean.

Estimated average glucose (eAG)
7 mmol/L
A1C in IFCC units
42 mmol/mol

See the step-by-step solution ↓

Step-by-step solution

  1. Use the ADAG formula: multiply the A1C percent by 28.7, then subtract 46.7. That gives average glucose in mg/dL

    28.7×6−46.7=125.5 mg/dL

  2. Change mg/dL to mmol/L by dividing by 18.0156, the mg/dL in 1 mmol/L of glucose

    125.5 mg/dL18.0156=6.966 mmol/L

  3. Change A1C from percent to mmol/mol, the unit many labs outside the US use: subtract 2.152, then divide by 0.09148

    (6−2.152)0.09148=42.06 mmol/mol

Test yourself

20 quick questions built from this calculator's formula: work out results, predict what happens when an input changes, and work backward from an answer. Every answer comes with the working.

Please note: This calculator gives a general screening estimate, not a diagnosis. Talk to a qualified healthcare professional about your individual health.

What this calculator does

Find out what an A1C result means in everyday glucose numbers. An A1C test shows roughly how high your blood sugar has been over the past two to three months. Your lab reports it as a percent, or in mmol/mol in many countries. This calculator turns it into estimated average glucose, or eAG. That is in the same units a home glucose meter shows: mg/dL or mmol/L.

It also works the other way. Enter an average glucose, for example from a meter or sensor report, and it shows the A1C that usually goes with it. The calculator only converts numbers. It does not say whether a result is good or bad for you. Talk with your doctor about what your own results mean.

Where it's used

Why this math matters outside the classroom:

  • Reading a lab report. A patient with an A1C of 6.8% works out 28.7 × 6.8 − 46.7, which is about 148 mg/dL of average glucose.
  • Rearranging a formula. Algebra students solve eAG = 28.7 × A1C − 46.7 for A1C and get A1C = (eAG + 46.7) ÷ 28.7.
  • Unit conversion. A nursing student divides 148.46 mg/dL by 18.0156 to get about 8.2 mmol/L for an international chart.
  • Lab units abroad. A traveler reads 53 mmol/mol on a foreign lab report and converts it to about 7.0% to compare with older results.
  • Linear models. A statistics class sees that each 1-point rise in A1C adds 28.7 mg/dL, the slope of the ADAG line.

Grade level and standards: Grade 9; Common Core State Standards for Mathematics HSA.CED.A.4. © Copyright 2010. National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved.

How to use it

  1. Choose whether you are starting from an A1C or from an average glucose.
  2. Enter the number and pick its unit: percent or mmol/mol for A1C, mg/dL or mmol/L for glucose.
  3. Read the converted values. The main result uses the same unit system you typed in.
  4. Open the steps to see each multiplication and division.

What the inputs mean

A1C result
Labs in the US report A1C as a percent, such as 6.2%. Many other countries report it in mmol/mol, such as 44 mmol/mol. Both describe the same test.
Average blood glucose
Use an average taken over many weeks, such as a sensor's 90-day report. A single finger-stick reading is not an average and can swing a lot within a day.

Formula and method

eAG (mg/dL) = 28.7 × A1C (%) − 46.7
A1C (%) = (eAG + 46.7) ÷ 28.7
eAG (mmol/L) = eAG (mg/dL) ÷ 18.0156
A1C (mmol/mol) = (A1C (%) − 2.152) ÷ 0.09148

A1C measures how much of the hemoglobin in your red blood cells has glucose stuck to it. Hemoglobin is the protein that carries oxygen. Red blood cells live for a few months, so the result reflects your glucose over that time.

The first formula comes from the A1C-Derived Average Glucose (ADAG) study, published in 2008. Researchers compared A1C with frequent glucose readings from several hundred adults. They found that a straight line fits the pair well. The second formula is the same line solved for A1C.

To change mg/dL into mmol/L, the calculator divides by 18.0156. That number comes from the weight of one mole of glucose, 180.156 grams. The last formula is the agreed conversion between the US percent scale and the international mmol/mol scale.

Worked example

A lab report shows an A1C of 6.8%.

  1. Average glucose in mg/dL: 28.7 × 6.8 − 46.7 = 148.46 mg/dL.
  2. In mmol/L: 148.46 ÷ 18.0156 = 8.241 mmol/L.
  3. A1C in mmol/mol: (6.8 − 2.152) ÷ 0.09148 = 50.81 mmol/mol.

Result: An A1C of 6.8% matches an estimated average glucose of about 148 mg/dL (8.2 mmol/L). The same A1C is about 51 mmol/mol.

Understanding the result

The eAG is the average glucose that people with that A1C had in the study. Your own average can be a bit higher or lower than the estimate. That's normal variation between people, not a mistake in your meter.

Each step of 1 percentage point in A1C adds 28.7 mg/dL (about 1.6 mmol/L) to the estimated average. So small changes in A1C are bigger changes in daily glucose than they look.

A1C and eAG are averages. They can't show highs and lows within a day. Your doctor will look at them together with your other results and your history.

Assumptions and limitations

  • The ADAG straight-line formula applies to you. It was built from adults, mostly with and some without diabetes.
  • Red blood cells live a typical length of time, so A1C reflects the past two to three months.
  • Glucose converts at 18.0156 mg/dL per mmol/L, from the molar mass of glucose.
  • It does not diagnose anything or tell you what your target should be. Only your doctor can interpret your results.
  • Some conditions change how long red blood cells live, such as certain anemias, recent blood loss or pregnancy. Some hemoglobin variants also affect the test. In these cases, A1C may not match average glucose well.
  • Results near the ends of the 3% to 20% range are less certain, because the study had few people there.

Frequently asked questions

What does A1C measure?

It measures the share of hemoglobin in your red blood cells that has glucose attached. The more glucose in your blood over time, the more attaches. Because red blood cells last a few months, it reflects that whole period, not just today.

Why doesn't my meter average match my eAG?

The eAG is an estimate from a study group, and people differ. A meter average also depends on when you test. Readings taken mostly before meals miss the higher numbers after meals. A gap between the two is common, and it's worth mentioning to your doctor.

How do I convert A1C between percent and mmol/mol?

Subtract 2.152 from the percent, then divide by 0.09148. For example, 7% becomes (7 − 2.152) ÷ 0.09148, which is about 53 mmol/mol. To go back, multiply by 0.09148 and add 2.152.

What should I do with my result?

Talk with your doctor about it. They can explain what it means for you, together with your other tests, your health history and any symptoms. This calculator only converts between units.

How this calculator is checked

Method: ADAG regression, Nathan DM et al., "Translating the A1C assay into estimated average glucose values", Diabetes Care 2008: eAG (mg/dL) = 28.7 × A1C − 46.7, and its inverse. mg/dL ÷ 18.0156 = mmol/L, from the molar mass of glucose (180.156 g/mol). NGSP–IFCC master equation: NGSP (%) = 0.09148 × IFCC (mmol/mol) + 2.152. The calculation is covered by automated tests with known reference values and edge cases. Last updated 2026-10-26. Found a problem? Tell us.

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