A1C to Average Glucose Calculator
Convert an HbA1c percentage to estimated average glucose (eAG) in mg/dL and mmol/L using the ADAG study regression.
How it works
eAG (mg/dL) = 28.7 × A1C − 46.7 · eAG (mmol/L) = eAG(mg/dL) ÷ 18.0182 · IFCC A1C (mmol/mol) = (A1C% − 2.15) × 10.929
HbA1c reflects the fraction of haemoglobin that has become glycated, which rises with the average blood glucose over the preceding two to three months. The ADAG study fitted a straightforward linear relationship between A1C and mean glucose, letting a percentage be read as a familiar mg/dL or mmol/L figure. The estimate is a population average — individual red-cell lifespan, anaemia and certain haemoglobin variants can make a person’s true average glucose run higher or lower than the formula predicts.
Worked example
For an HbA1c of 7.0%: eAG = 28.7 × 7.0 − 46.7 = 200.9 − 46.7 = 154.2 mg/dL, which divided by 18.0182 is about 8.6 mmol/L — the widely quoted "7% ≈ 154 mg/dL" pairing.
Frequently asked questions
What does estimated average glucose mean?
It translates your A1C percentage into the average blood-glucose level it corresponds to, in the same units your meter shows. It makes a lab A1C easier to relate to day-to-day readings.
Why might my meter average differ from my eAG?
eAG is a statistical average from a study population. Factors like the lifespan of your red blood cells, anaemia, pregnancy and haemoglobin variants can shift your real average away from the formula’s estimate.
What A1C indicates diabetes?
Generally, below 5.7% is normal, 5.7–6.4% is prediabetes, and 6.5% or above on two tests indicates diabetes. Diagnosis is made by a clinician using the full context.
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Educational estimate using standard published formulas — not medical advice, a diagnosis, or a substitute for clinical judgement. Dosing, diagnosis and treatment must be decided by a qualified clinician using validated tools and the full clinical picture.