A1C Calculator: A1C to Average Glucose and Back
Convert an A1C percentage to estimated average glucose in mg/dL and mmol/L, or an average glucose back to A1C, using the published ADAG equation.
Estimated average glucose (eAG) in mg/dL is 28.7 times the A1C, minus 46.7. An A1C of 7% therefore matches an average of about 154 mg/dL, or 8.6 mmol/L. An A1C of 5.7%, where the lab range for prediabetes starts, matches about 117 mg/dL, and 6.5%, where the diabetes range starts, about 140 mg/dL. The equation runs backwards too: 154 mg/dL gives 7.0%.
This calculator converts numbers for general education; it is not medical advice, a diagnosis or a substitute for care from a qualified health professional. The estimate comes from a population regression, so your own average glucose can differ, and A1C can be inaccurate with anemia, kidney or liver disease, recent blood loss or transfusion, sickle cell disease, some hemoglobin variants, hemodialysis, or erythropoietin treatment. Do not change medication, diet or insulin based on this page; talk to your doctor or diabetes care team about your results.
An A1C from 4.0 to 20.0 percent, as printed on a lab report, with at most one decimal.
Estimated average glucose at A1C 7.0%
154 mg/dL
- In mmol/L
- 8.6 mmol/L
- A1C range
- 6.5% or above, the range the NIDDK lists as diabetes
An estimate from the ADAG study's regression across many people; your own average can differ. Only a lab A1C, confirmed by a second test, is used to diagnose diabetes.
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About the A1C Calculator
A1C measures the share of hemoglobin in red blood cells that has glucose attached, and because those cells live for months, it reflects average blood sugar over roughly the past three months rather than on the day of the test. The equation on this page comes from the A1c-Derived Average Glucose (ADAG) study, published in Diabetes Care in 2008, which compared lab A1C results with frequent glucose readings from the same people and fitted a straight line: eAG in mg/dL is 28.7 times the A1C minus 46.7, with an R-squared of 0.84, and in mmol/L it is 1.5944 times the A1C minus 2.594. The calculator matches the study's conversion table at 5% to 12%, from 97 mg/dL to 298 mg/dL. The ranges shown are the standard ones for a lab A1C: below 5.7% normal, 5.7% to 6.4% prediabetes, and 6.5% or above diabetes. A single number is not a diagnosis; a diagnosis rests on a lab test confirmed by a second measurement. A1C can also read falsely high or low with iron-deficiency anemia, kidney or liver disease, recent blood loss or transfusion, sickle cell disease, some other hemoglobin variants, hemodialysis, or treatment with erythropoietin.
Frequently asked questions
How do you convert A1C to average blood sugar?+
Multiply the A1C by 28.7 and subtract 46.7 to get mg/dL, or multiply by 1.5944 and subtract 2.594 for mmol/L. At 7%, that is 200.9 minus 46.7, about 154 mg/dL. Each full point of A1C adds 28.7 mg/dL to the estimate.
What A1C matches an average glucose of 154 mg/dL?+
About 7.0%. The calculator solves the same equation in reverse: add 46.7 to the average glucose and divide by 28.7. Choose Average glucose to A1C in the Convert menu and enter the number from your meter or sensor report in mg/dL or mmol/L.
Why doesn't my meter or sensor average match my lab A1C?+
Because the equation is a line fitted across many people, and individuals sit above or below it. The ADAG paper's own table gives a wide band around each estimate: at an A1C of 7%, its 95% interval runs from 123 to 185 mg/dL. A meter average also depends on when you test, while A1C weighs every hour of the past few months.
What do the A1C ranges mean?+
For a lab A1C, below 5.7% is the normal range, 5.7% to 6.4% is the prediabetes range, and 6.5% or above is the diabetes range. The calculator shows which range a number falls in so you can read a report, but it cannot tell you whether you have diabetes; that takes a lab test, confirmed by a second one, and a clinician's judgment.
Equation and conversion table: Nathan DM et al., ADAG Study Group, "Translating the A1C Assay Into Estimated Average Glucose Values," Diabetes Care 2008;31(8):1473-1478. Ranges: National Institute of Diabetes and Digestive and Kidney Diseases, The A1C Test & Diabetes.
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