A1C Calculator

Convert HbA1c between % and mmol/mol, turn A1C into estimated average blood sugar in mg/dL or mmol/L, and see UK and US ranges.

Reviewed by Dany, RightSums team · Updated

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health · Daily life · UK & US

Enter an HbA1c result in % or mmol/mol, or an average blood sugar in mg/dL or mmol/L, and the calculator converts it to every other unit. Average glucose uses the ADAG study formula from Diabetes Care (2008): 28.7 × A1C − 46.7 in mg/dL. The mmol/mol figure uses the NGSP master equation. You can compare the result with UK ranges from Diabetes UK (below 42, 42 to 47, 48 or above mmol/mol) or US ranges from the CDC and ADA (below 5.7%, 5.7% to 6.4%, 6.5% or above). A table shows the study's 95% ranges. This is an estimate, not a diagnosis or medical advice: use your own lab results and talk to your GP, doctor or diabetes team.

Accepted inputs

  • HbA1c in % (DCCT/NGSP)
  • HbA1c in mmol/mol (IFCC)
  • Estimated average glucose in mg/dL
  • Estimated average glucose in mmol/L
  • UK or US ranges to compare with

Outputs

  • HbA1c in % and mmol/mol
  • Estimated average glucose in mg/dL and mmol/L
  • Range: normal, prediabetes or diabetes range (UK or US)
  • ADAG study table with 95% ranges for A1C 5% to 12%

How to use the A1C Calculator

  1. Choose what you want to convert, such as an HbA1c result in % or mmol/mol, or an average glucose in mg/dL or mmol/L, and type in the number.
  2. The calculator turns it into A1C % first, using the NGSP master equation for mmol/mol and the ADAG study formulas for average glucose.
  3. It then works out every other unit, so 7% shows as 53 mmol/mol, 154 mg/dL and 8.6 mmol/L.
  4. Finally it compares the result with UK or US ranges and shows the ADAG table, which gives the range of average glucose seen at each A1C level.

Frequently asked questions

How do I convert A1C to average blood sugar?

Multiply your A1C by 28.7 and take away 46.7 to get estimated average glucose in mg/dL, the formula from the ADAG study. An A1C of 7% gives 154 mg/dL, or 8.6 mmol/L using the study's mmol/L formula (1.5944 × A1C − 2.594). Your real average can differ: at 7%, people in the study ranged from 123 to 185 mg/dL.

How do I convert HbA1c from % to mmol/mol?

Take 2.152 from the % figure and divide by 0.09148, which is the NGSP master equation turned round. So 6.5% is 47.5, which rounds to 48 mmol/mol, and 7% is 53 mmol/mol. Going the other way, 48 mmol/mol is 6.5% and 42 mmol/mol is 6.0%.

What HbA1c level is prediabetes?

In the UK, Diabetes UK puts prediabetes at 42 to 47 mmol/mol and diabetes at 48 mmol/mol or above. In the US, the CDC and ADA use 5.7% to 6.4% for prediabetes and 6.5% or above for diabetes. The lines differ a little: 5.7% is 39 mmol/mol, which is still in the UK normal range.

What A1C is my average glucose of 150 mg/dL?

An average glucose of 150 mg/dL works out at an A1C of about 6.9%, or 51 mmol/mol, using the ADAG formula in reverse. In mmol/L, an average of 8.0 gives about 6.6%, or 49 mmol/mol. This only works with a true average over weeks, such as from a sensor, not a single finger-prick reading.

Can this calculator tell me if I have diabetes?

No. It converts numbers and shows where they fall, but a single estimate cannot diagnose anything. Diabetes UK says a result of 48 mmol/mol without symptoms should be repeated. The CDC says severe anaemia, kidney failure, liver disease, some blood disorders, blood loss and early or late pregnancy can make HbA1c read wrongly. Talk to your GP, doctor or diabetes team about your own test results.

Sources

The rates and rules in this tool come from:

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