By Zencalcy Editorial TeamLast reviewed About us
This calculator reverses the usual A1c-to-glucose relationship: it takes an average glucose value and estimates the A1c percentage that would typically accompany it. It is useful when you have a reliable average from a meter or continuous sensor but want to understand what lab result it might correspond to. The output is an estimate, not a substitute for a lab test.
Estimate A1c from an average glucose value.
A1c(%) = (average glucose(mg/dL) + 46.7) ÷ 28.7
This is the algebraic inverse of the ADAG eAG equation. It assumes your average glucose and A1c follow the population relationship. Haemoglobin variants, anaemia, kidney disease and recent blood loss can make a lab A1c disagree with the estimate.
| Symbol | Meaning |
|---|---|
| A1c | Estimated glycated haemoglobin percentage. |
| average glucose | Your average blood glucose in mg/dL. |
| 46.7 and 28.7 | ADAG coefficients rearranged to solve for A1c. |
A1c = (154.2 + 46.7) ÷ 28.7 = 200.9 ÷ 28.7 = 7.0%. An average of 8.56 mmol/L converts to 154.2 mg/dL and gives the same estimate. An average of 126 mg/dL gives (126 + 46.7) ÷ 28.7 = 6.0%.
The inverse ADAG equation is useful for connecting two ways of describing glucose control, but it is not a diagnostic tool. A1c is shaped by average glucose and by how long red blood cells survive. If red cells turn over faster than usual, A1c can look lower than the glucose history suggests; if they live longer, it can look higher. Iron deficiency, recent transfusion, pregnancy and some haemoglobin traits are familiar examples. The estimate also depends on the quality of the average you provide. Sensor data with good coverage is more representative than a handful of fingersticks. Treat the result as a prompt to discuss the whole picture with a clinician, including time in range, hypoglycaemia and how you feel, rather than as a replacement for the laboratory value.
Continue with the Blood Sugar Converter, Estimated Average Glucose Calculator, or the HOMA-IR Calculator — or browse more diabetes tools and all health calculators.
It is a reasonable population estimate but not a lab measurement. The relationship varies between individuals, and factors such as red blood cell lifespan, anaemia and haemoglobin variants can shift the real A1c away from the prediction.
These tools convert or screen laboratory values using published formulas. They do not diagnose diabetes, insulin resistance or ketoacidosis, and they do not calculate an insulin dose. Laboratory methods vary; confirm results with the reporting lab and a clinician. DKA symptoms need urgent medical care.
Reference material used to build and check this calculator:
Last reviewed: September 2026. See how we build and check every tool on the about page.
Content updated: September 2026