Estimated Average Glucose to A1C Calculator
Convert estimated average glucose (eAG in mg/dL or mmol/L) back to an approximate HbA1c percentage using the ADA consensus formula.
How to use this tool
- Enter average glucose in the fields above.
- Results update instantly as you type — or click Calculate.
- Read your estimated hba1c and the full breakdown beneath it.
Educational estimate — not medical advice. Consult a clinician.
This is the algebraic inverse of the ADA A1C→eAG formula: A1C = (eAG + 46.7) ÷ 28.7. Useful when you know your average CGM reading and want a ballpark A1C before your next lab draw.
Formula
Estimated HbA1c (%) = (eAG (mg/dL) + 46.7) ÷ 28.7
This is the inverse of the ADA consensus equation (Nathan et al., 2008).
How it works
This calculator reverses the ADA consensus formula to estimate an approximate HbA1c percentage from an average blood glucose value in mg/dL. It is the algebraic inverse of the A1C-to-eAG conversion: adding 46.7 to the average glucose and dividing by 28.7 recovers the A1C.
Because the calculation uses a population-derived average, the result is an estimate rather than a certified laboratory measurement. Conditions that alter red cell lifespan — haemolytic anaemia, iron deficiency, recent transfusion — can cause actual A1C to diverge from this estimate.
Worked example
Worked example
- Input: average glucose = 154 mg/dL.
- Add 46.7: 154 + 46.7 = 200.7.
- Divide by 28.7: 200.7 ÷ 28.7 = 6.99%.
Estimated HbA1c: 6.99%
Key terms
- eAG (Estimated Average Glucose)
- A glucose value in mg/dL or mmol/L representing the average concentration implied by an HbA1c reading over the prior 2–3 months.
- HbA1c
- Glycated haemoglobin; the percentage of haemoglobin carrying a glucose molecule, used to monitor long-term blood-sugar control in diabetes management.
- Algebraic inverse
- Rearranging an equation to solve for a previously calculated input; here, solving for A1C given eAG rather than eAG given A1C.
- Blood glucose target (type 2 diabetes)
- Many guidelines suggest an HbA1c target of around 7% (eAG ~154 mg/dL) for most non-pregnant adults with type 2 diabetes.
- Self-monitoring of blood glucose (SMBG)
- Home glucose testing using a finger-prick meter; readings are in mg/dL or mmol/L, making the eAG-to-A1C conversion useful for comparing meter averages to lab tests.
Frequently asked questions
- How accurate is this estimate?
- The formula is validated at the population level; individual A1C can differ by ~0.3–0.5% due to red blood cell turnover, haemoglobin variants, and other factors. Only a certified lab test gives your actual HbA1c.
- What units does this calculator accept?
- This tool accepts mg/dL. To convert from mmol/L, multiply by 18.018 (e.g., 8.56 mmol/L × 18.018 ≈ 154 mg/dL).