Glucose to A1C Calculator
Your meter or sensor shows an average glucose, and your lab report shows A1C. This page links the two. The formula gives an estimate, not a test result.
Quick answer: Add 46.7 to the average glucose in mg/dL, then divide by 28.7. For example, an average glucose of 100 mg/dL is 5.111 %, an average glucose of 154 mg/dL is 6.993 % and an average glucose of 200 mg/dL is 8.596 %.
The glucose to A1C formula
The estimated average glucose is 28.7 times the A1C minus 46.7, in mg/dL (Wikipedia: Glycated hemoglobin).
Turn it around, and A1C equals the glucose plus 46.7, divided by 28.7.
Take an average glucose of 100 mg/dL. (100 + 46.7) ÷ 28.7 gives 5.111 %.
Take an average glucose of 154 mg/dL. (154 + 46.7) ÷ 28.7 gives 6.993 %.
Average glucose to A1C
Average glucose in mg/dL. For mmol/L, multiply by 18.016 first.
A1C is the estimated result, in percent.
The last column shows the same glucose in mmol/L.
How to convert glucose to A1C step by step
- Enter the average glucose in mg/dL.
- If you have mmol/L, multiply by 18.016 first.
- Read the estimated A1C in percent.
- Remember it is an estimate only.
Example 1: an average glucose of 100 mg/dL
- Start with an average glucose of 100 mg/dL.
- (100 + 46.7) ÷ 28.7 = 5.111.
- The result is 5.111 %.
an average glucose of 100 mg/dL = 5.111 %
Example 2: an average glucose of 154 mg/dL
- Start with an average glucose of 154 mg/dL.
- (154 + 46.7) ÷ 28.7 = 6.993.
- The result is 6.993 %.
an average glucose of 154 mg/dL = 6.993 %
Example 3: an average glucose of 200 mg/dL
- Start with an average glucose of 200 mg/dL.
- (200 + 46.7) ÷ 28.7 = 8.596.
- The result is 8.596 %.
an average glucose of 200 mg/dL = 8.596 %
The formula is an approximate mapping with wide confidence intervals, so a single reading cannot stand in for a lab A1C (Wikipedia: Glycated hemoglobin).
glucose to A1C conversion table
| Average glucose (mg/dL) | Estimated A1C (%) | Glucose (mmol/L) |
|---|---|---|
| an average glucose of 80 mg/dL | 4.415 % | 4.44 mmol/L |
| an average glucose of 100 mg/dL | 5.111 % | 5.551 mmol/L |
| an average glucose of 117 mg/dL | 5.704 % | 6.494 mmol/L |
| an average glucose of 126 mg/dL | 6.017 % | 6.994 mmol/L |
| an average glucose of 140 mg/dL | 6.505 % | 7.771 mmol/L |
| an average glucose of 154 mg/dL | 6.993 % | 8.548 mmol/L |
| an average glucose of 200 mg/dL | 8.596 % | 11.101 mmol/L |
| an average glucose of 250 mg/dL | 10.338 % | 13.877 mmol/L |
The highlighted row is the default of the calculator. The last column gives mmol/L.
A quick mental shortcut for glucose to A1C
Add about 47 to the glucose, then divide by 29.
So a glucose of 154 gives about 7.
What average glucose measures
Average glucose is the mean of many readings over time, in mg/dL.
One fingerstick is not an average.
What A1C measures
A1C is the share of hemoglobin that has glucose attached, in percent.
It is a lab test, so this page can only estimate it.
Worked example: an average glucose of 100 mg/dL
An average glucose of 100 mg/dL gives 5.1115 %.
The same inputs give 5.5506 mmol/L in the last column.
Worked example: an average glucose of 154 mg/dL
An average glucose of 154 mg/dL gives 6.993 %.
The same inputs give 8.548 mmol/L in the last column.
Worked example: an average glucose of 200 mg/dL
An average glucose of 200 mg/dL gives 8.5958 %.
The same inputs give 11.101 mmol/L in the last column.
Why it is an estimate
The source gives wide confidence intervals. For example, 6 percent A1C maps to 100 to 152 mg/dL (Wikipedia: Glycated hemoglobin).
So two people with the same A1C can have different average glucose.
When A1C can mislead
Blood loss, anemia, transfusion and some kidney or liver disease can make A1C unreliable (Wikipedia: Glycated hemoglobin).
In those cases, other tests may be used, so ask your clinician.
Going the other way
To go from A1C to glucose, multiply the A1C by 28.7 and subtract 46.7.
So an A1C of 7 gives about 154 mg/dL.
Check your answer
Your A1C times 28.7 minus 46.7 should give back your glucose.
Try 6.99 times 28.7 minus 46.7, which gives about 154.
Quick conversion answers
| Conversion | Result |
|---|---|
| an average glucose of 100 mg/dL | 5.111 % |
| an average glucose of 117 mg/dL | 5.704 % |
| an average glucose of 140 mg/dL | 6.505 % |
| an average glucose of 154 mg/dL | 6.993 % |
| an average glucose of 200 mg/dL | 8.596 % |
| an average glucose of 250 mg/dL | 10.338 % |
Where this conversion is used
Meters and labs report blood glucose in different units.
Lab reports show A1C as a percent of hemoglobin.
Students practise formulas.
People compare meter averages with lab reports.
Common mistakes to avoid
- Using a single reading. The formula needs an average of many readings.
- Using mmol/L directly. Multiply by 18.016 first to get mg/dL.
- Treating it as a lab result. It is only an estimate.
- Rounding too early. The answer for an average glucose of 250 mg/dL is 10.338 %. Cut it to 10 % and you are off by about 3.3 percent, and the gap grows if you reuse it.
Related converters
- mg/dL to A1C
- cholesterol mmol/L to mg/dL
- mg/dL to µmol/L
- g/L to mmol/L
- A1C to average blood sugar calculator
Example: an average glucose of 117 mg/dL
An average glucose of 117 mg/dL gives 5.7038 %.
The same inputs give 6.4942 mmol/L in the last column.
Example: an average glucose of 126 mg/dL
An average glucose of 126 mg/dL gives 6.0174 %.
The same inputs give 6.9938 mmol/L in the last column.
Frequently asked questions
How do I find %?
A1C (%) = (glucose in mg/dL + 46.7) ÷ 28.7.
What is the answer for an average glucose of 100 mg/dL?
5.1115 %.
What is the answer for an average glucose of 154 mg/dL?
6.993 %.
Is this the same as a lab A1C?
No. It is an estimate from a formula, and a lab test is the real result.
How do I use mmol/L?
Multiply by 18.016 to get mg/dL, then use the formula.
Is this medical advice?
No. It checks the maths only. Ask your clinician about your result.
Sources
- Wikipedia: Glycated hemoglobin (en.wikipedia.org)
