Estimated Average Glucose CalculatorFree online fitness & health calculator — instant results, no sign-up
Convert HbA1c into estimated average glucose using the ADAG relationship.
For general information only. This is not medical advice, diagnosis, dosing guidance or a treatment recommendation. Talk to a doctor or other qualified health professional about your health, pregnancy, or diet.
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About the Estimated Average Glucose Calculator
The Estimated Average Glucose Calculator converts HbA1c (%) into estimated average glucose using the A1c-Derived Average Glucose (ADAG) relationship. It reports the estimate in both mg/dL and mmol/L, helping you relate an HbA1c result to average glucose over roughly the past 2–3 months. This tool provides educational estimates for adults, not a diagnosis or treatment recommendation.
- HbA1c (%)
- HbA1c is the percentage of hemoglobin with glucose attached, entered as a percent using your laboratory result; the default is 6.5.
Formula and method
G = 28.7 × A − 46.7; M = G ÷ 18.018. With A = 6.5: G = 28.7 × 6.5 − 46.7 = 139.85 mg/dL, and M = 139.85 ÷ 18.018 ≈ 7.76 mmol/L.
- AHbA1c entered as a percentage, such as the default 6.5.
- GEstimated average glucose in mg/dL calculated using the ADAG relationship.
- MEstimated average glucose in mmol/L; 18.018 is the glucose unit-conversion factor from mmol/L to mg/dL.
Multiply the entered HbA1c percentage by 28.7, then subtract 46.7 to estimate average glucose in mg/dL. Divide that unrounded estimate by 18.018 to convert it to mmol/L. Display both results to two decimal places alongside the cautionary notes.
Worked example
These are the calculator's starting values and the results it actually produces for them.
Inputs
- HbA1c6.5 %
Results
- Estimated average glucose139.85 mg/dL
- Estimated average glucose7.76 mmol/L
- NoteHbA1c can be misleading with altered red cell turnover or some hemoglobin variants.
- NoteEducational estimate for adults; not a diagnosis or treatment recommendation.
How to use the Estimated Average Glucose Calculator
- 1Find the HbA1c percentage on your laboratory report; do not enter an HbA1c value reported in mmol/mol.
- 2Enter the percentage in the HbA1c (%) field, or leave the default value of 6.5 to view the worked example.
- 3Run the calculation to convert HbA1c into estimated average glucose using the ADAG equation.
- 4Read the result in your preferred glucose unit: the default gives 139.85 mg/dL and 7.76 mmol/L.
- 5Review both notes before interpreting the estimate, and discuss unexpected results with a healthcare professional.
Reading your result
The 'Estimated average glucose' row showing 139.85 mg/dL is the average glucose predicted from the default HbA1c of 6.5%. The row showing 7.76 mmol/L expresses the same estimate in another unit; it is not a separate measurement. The note 'HbA1c can be misleading with altered red cell turnover or some hemoglobin variants.' flags circumstances that can make this conversion unreliable. The note 'Educational estimate for adults; not a diagnosis or treatment recommendation.' means the result should not be used alone to diagnose diabetes or change medication, diet, or glucose targets.
Limitations
The ADAG equation describes a population-level relationship, so an individual's actual average glucose may differ from the estimate. HbA1c reflects roughly the preceding 2–3 months, with more influence from recent weeks, and does not reveal glucose spikes, low-glucose episodes, or daily variability. Altered red cell turnover, recent blood loss or transfusion, some anemias, and some hemoglobin variants can affect HbA1c or its measurement. Pregnancy and certain medical conditions may also complicate interpretation. This educational adult estimate is not a fasting glucose prediction or a substitute for measured glucose; two-decimal output formatting does not imply that level of clinical precision.
Common questions
Why does an HbA1c of 6.5% produce 139.85 mg/dL?+
The ADAG relationship is estimated average glucose in mg/dL = 28.7 × HbA1c (%) − 46.7. Substituting 6.5 gives 139.85 mg/dL, which converts to approximately 7.76 mmol/L.
Can I enter HbA1c reported in mmol/mol?+
No. This calculator expects HbA1c as a percentage. HbA1c in mmol/mol must first be converted to the percentage reporting scale; it is also distinct from the glucose output unit mmol/L.
Why might this estimate differ from my glucose meter or continuous glucose monitor average?+
The calculator predicts average glucose from HbA1c rather than averaging glucose readings. Differences can reflect the monitoring period, which readings were captured, individual biology, or conditions affecting red cells or HbA1c measurement.
Does the result tell me my fasting glucose or whether I have diabetes?+
No. Estimated average glucose represents glucose across the day over time, not a fasting measurement. Diagnosis requires clinical interpretation of appropriate laboratory tests, and this conversion is not an independent diagnostic test.
Does the calculator save my information?+
Calculations run in your browser. While signed in, inputs and results are automatically recorded in account history; saving a result creates a separate saved record.
Further reading
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Results are estimates for informational purposes and are not financial, medical or legal advice.