Case 1
- Glucose unit
- mg/dL
- Average glucose
- 154
7.0%
Diabetes range
Open with these valuesA1C Calculator
7.0%
Result: 7.0 %Diabetes range
7.0
Estimated A1C is your average blood glucose in mg/dL plus 46.7, divided by 28.7 — the regression the ADA publishes. An average of 154 mg/dL (8.6 mmol/L) gives 7.0 %. It estimates a lab A1C from a mean; it does not replace one, and it says nothing about your highs and lows.
Worked examples
Case 2
- Glucose unit
- mg/dL
- Average glucose
- 114
5.6%
Normal range
Open with these valuesCase 3
- Glucose unit
- mmol/L
- Average glucose
- 8.6
7.0%
Diabetes range
Open with these valuesHow it's calculated
A1C = (average glucose in mg/dL + 46.7) / 28.7
- StepTake your average blood glucose over the past two to three months.
- StepMeasuring in mmol/L? Multiply by 18 to get mg/dL first.
- StepAdd 46.7 to that figure.
- ResultDivide by 28.7 — the result is the estimated A1C in percent.
What this number means
A1C reports the share of haemoglobin carrying glucose, and because red blood cells live about three months, it stands in for average glucose over that window. The ADAG study measured both in 507 people and fitted one line between them: average glucose in mg/dL equals 28.7 times A1C minus 46.7. This page runs that line backwards, so an average you already have becomes the A1C it corresponds to. At 154 mg/dL the arithmetic is (154 + 46.7) / 28.7 = 7.0 %. In mmol/L the same relationship is 1.5944 times A1C minus 2.5944, which is the mg/dL version divided by 18 — that is the factor the published table uses, not the molar 18.0182. Two limits are worth holding onto. First, this is an estimate of a lab test, not the lab test. The fit was tight but not perfect, and an individual A1C can sit either side of the line, so a measured value is what a clinician works from. Second, an average hides its own spread. The same 154 mg/dL can come from steady readings all day or from swings between 60 and 250, and those two are not the same situation even though they share an A1C. Conditions that shorten or lengthen red cell life — anaemia, recent transfusion, pregnancy, some haemoglobin variants — break the assumption behind the number entirely.
Linear regression analysis between the A1C and average glucose values provided the tightest correlations (AG mg/dl = 28.7 × A1C − 46.7, R² = 0.84, P < 0.0001), allowing calculation of an estimated average glucose for A1C values.
An estimate, not a diagnosis
The ranges shown are the ADA's thresholds for a measured, lab-run A1C. A figure estimated from your own meter readings is not that test and cannot diagnose anything. Only a clinician can.
Where the number stops working
A1C assumes a normal red blood cell lifespan. Anaemia, recent blood loss or transfusion, pregnancy, kidney disease and some haemoglobin variants all shift it away from your real average glucose.
The average hides the swings
Two people can share an A1C and live very different days — one steady, one swinging between lows and highs. Time in range, from a meter or a sensor, is the figure that separates them.
Germany reads A1C in mmol/mol
German labs report the IFCC unit. The NGSP master equation converts it: mmol/mol = (A1C % − 2.152) / 0.09148. A 7.0 % result is 53 mmol/mol.
Commonly misread
This number is my A1C.
It is the A1C your average glucose corresponds to on a published regression line. A lab measures the glycated haemoglobin itself, and the two can differ.
My estimate is 6.6 %, so I have diabetes.
The 6.5 % threshold applies to a measured A1C, and the ADA asks for confirmation before a diagnosis. An estimate from meter readings is a reason to get tested, not a result.
A good A1C means my glucose was fine all quarter.
An average says nothing about spread. Frequent lows and frequent highs cancel out into a reassuring mean that describes neither.
Reference table
| Range | A1C (%) |
|---|---|
| Normal range | < 5.7 |
| Prediabetes range | 5.7 – < 6.5 |
| Diabetes range | ≥ 6.5Your value |
Questions
How do you calculate A1C from average blood sugar?
Add 46.7 to your average glucose in mg/dL and divide by 28.7. That is the ADAG regression published by Nathan and colleagues in 2008 and used by the ADA. In mmol/L, multiply your average by 18 before you start.
What average blood sugar is an A1C of 7 %?
About 154 mg/dL, or 8.6 mmol/L. The ADA's published conversion table lists that pair directly.
What A1C level is considered normal?
The ADA puts a measured A1C below 5.7 % in the normal range, 5.7 to 6.4 % in the prediabetes range, and 6.5 % or above in the diabetes range. Those cut-offs describe a laboratory test, not an estimate from a glucose meter.
How accurate is an estimated A1C?
The ADAG regression fitted its 507 participants closely but not exactly, so an individual result can sit either side of the line. Anaemia, pregnancy, kidney disease and haemoglobin variants can move it further still.
Can I convert A1C back to average glucose?
Yes — switch the calculator to solve for average glucose, or multiply your A1C by 28.7 and subtract 46.7. An A1C of 8 % works out to 183 mg/dL, which is 10.2 mmol/L.
What is A1C in mmol/mol?
German and most European labs report the IFCC unit instead of a percentage. The NGSP master equation converts between them: mmol/mol = (A1C % − 2.152) / 0.09148, so 7.0 % is 53 mmol/mol.
Sources and last check
Information, not medical advice.