Glucose to A1C Calculator
Convert average glucose to estimated A1C or A1C to estimated average glucose using the ADA/ADAG relationship, with mg/dL and mmol/L support.
Convert an average blood glucose value to an estimated A1C, or convert a lab A1C result back to estimated average glucose (eAG) in mg/dL and mmol/L.
Estimated result
Use this glucose to A1C calculator to convert a long-term average blood glucose value into an estimated A1C percentage, or reverse the calculation and convert an A1C result into estimated average glucose (eAG). The calculator supports both mg/dL and mmol/L and uses the relationship published by the A1c-Derived Average Glucose (ADAG) Study and used by the American Diabetes Association.
Average glucose to A1C formula
The ADAG study compared laboratory A1C results with thousands of glucose measurements collected over approximately three months. The published relationship is:
eAG (mg/dL) = 28.7 × A1C − 46.7
Solving that equation for A1C gives the formula used by this average glucose to A1C calculator:
Estimated A1C = (average glucose in mg/dL + 46.7) ÷ 28.7
For example, an average glucose of 154 mg/dL gives:
(154 + 46.7) ÷ 28.7 ≈ 6.99%
That is why an A1C near 7% is commonly paired with an eAG near 154 mg/dL in ADA reference tables.
Blood glucose to A1C calculator: use an average, not a single reading
A blood glucose to A1C calculator is only meaningful when the glucose number represents a genuine average over time. A1C reflects average glucose exposure over roughly the previous two to three months, with more recent weeks having greater influence. A single fasting reading, one post-meal spike, or one low value cannot be converted into a reliable A1C.
If you use finger-stick readings, calculate a representative average from many measurements. If you use a continuous glucose monitor, the device’s reported mean glucose is more suitable for this arithmetic than one spot reading. A CGM may also report Glucose Management Indicator (GMI), which is a separate estimate and should not be assumed to equal a laboratory A1C exactly.
Convert glucose to A1C in mg/dL or mmol/L
The calculator accepts U.S. glucose units in mg/dL and international units in mmol/L. Internally, mmol/L is converted to mg/dL before the ADAG equation is applied. The glucose-unit conversion is approximately:
mg/dL = mmol/L × 18.0182
So an average glucose of about 8.55 mmol/L is approximately 154 mg/dL and corresponds to an estimated A1C near 7% under the ADAG relationship.
Average blood glucose to A1C examples
This average blood glucose to A1C calculator uses the same ADAG equation for any representative long-term average entered within the supported range.
| Average glucose | Approx. mmol/L | Estimated A1C |
|---|---|---|
| 126 mg/dL | 7.0 mmol/L | about 6.0% |
| 154 mg/dL | 8.5 mmol/L | about 7.0% |
| 183 mg/dL | 10.2 mmol/L | about 8.0% |
| 212 mg/dL | 11.8 mmol/L | about 9.0% |
| 240 mg/dL | 13.3 mmol/L | about 10.0% |
These are estimates from the population relationship, not substitutes for laboratory testing.
Why estimated A1C can differ from a lab result
The ADAG equation is a regression relationship, so individual results can differ. NIDDK notes that A1C can be affected by conditions that alter red-blood-cell life span or hemoglobin. Examples include recent blood loss or transfusion, sickle cell disease and other hemoglobin disorders, iron-deficiency anemia, kidney failure, liver disease, erythropoietin treatment, and pregnancy. If an estimated result and a laboratory A1C do not agree, the laboratory result and clinical context should be reviewed with a healthcare professional.
A1C reference ranges are not a diagnosis from this calculator
For laboratory testing, NIDDK and CDC describe A1C below 5.7% as the usual normal range, 5.7% to 6.4% as the prediabetes range, and 6.5% or above as the diabetes range when appropriate diagnostic criteria are met. Diagnosis generally requires confirmation unless clear symptoms are present. An estimated A1C produced from average glucose should not be used to diagnose diabetes or prediabetes.
Frequently asked questions
How accurate is an average glucose to A1C calculator?
It is useful for estimating the population-level relationship between average glucose and A1C, but it cannot predict an individual’s laboratory A1C perfectly. The original ADAG study reported a strong but not perfect relationship, so individual variation is expected.
Can I use one blood glucose reading to estimate A1C?
No. A1C represents long-term glucose exposure. One reading can be affected by food, exercise, illness, stress, medication, and time of day.
What is the difference between A1C and eAG?
A1C is a laboratory percentage based on glycated hemoglobin. eAG translates that percentage into the same average-glucose units used by meters and CGMs. The calculator can work in either direction.
Is this a convert glucose to A1C calculator for both mg/dL and mmol/L?
Yes. Enter the average in either unit and the calculator shows both units plus the estimated A1C.
Why does my CGM average not match my laboratory A1C?
CGM mean glucose and laboratory A1C measure related but different things, and individual red-blood-cell biology can change the relationship. CGM systems may also report GMI, which is not identical to A1C.
Methodology and sources
This calculator uses the ADAG relationship published in Diabetes Care and presented by the American Diabetes Association: eAG = 28.7 × A1C − 46.7. The equation is algebraically rearranged for glucose-to-A1C conversion. NIDDK and ADA guidance is used for the discussion of A1C interpretation and limitations. The result is an educational estimate and is not a diagnosis, treatment target, or replacement for an NGSP-certified laboratory A1C test.