A1C to Average Blood Glucose Calculator

A1c (glycated haemoglobin) reflects the share of your haemoglobin that has sugar attached to it, which tracks your average blood glucose over the roughly two-to-three-month lifespan of a red blood cell. In 2008 the A1c-Derived Average Glucose (ADAG) study, published in Diabetes Care, measured continuous and frequent glucose readings in 507 participants and fitted a straight-line relationship between A1c and mean glucose with a correlation of R = 0.92. That single regression is what this tool computes.

1. A1c → average glucose (mg/dL): eAG = 28.7 × A1c − 46.7. An A1c of 7% gives 28.7 × 7 − 46.7 = 154 mg/dL.
2. mg/dL → mmol/L:divide by 18.0 (the ADA convention, from glucose's molar mass of ≈ 180.16 g/mol). So 154 mg/dL ÷ 18 = 8.6 mmol/L. Sri Lankan lab reports usually quote mmol/L, while glucometers and US references often use mg/dL — the tool shows both.
3. Average glucose → A1c (reverse): rearrange step one to A1c = (eAG + 46.7) ÷ 28.7. If you entered mmol/L it is first multiplied by 18.0 to get mg/dL.
4. ADA category from A1c: below 5.7% is normal, 5.7% to 6.4% is prediabetes, and 6.5% or higher meets the diabetes threshold — the adult, non-pregnant criteria from the ADA Standards of Care.

Nothing is rounded until the moment of display (A1c to one decimal, mg/dL to the nearest whole number, mmol/L to one decimal), so the figures stay internally consistent. As an independent credibility check, the calculator reproduces every value in the ADA's own published eAG/A1C conversion table — A1c 5%→97, 6%→126, 7%→154, 8%→183, 9%→212, 10%→240 mg/dL — and that check runs automatically on each build. This is lab A1c only: it is not the Glucose Management Indicator (GMI) used with continuous glucose monitors, which follows a different regression.

• Nathan DM et al. — Translating the A1C Assay Into Estimated Average Glucose Values (Diabetes Care, 2008)
• American Diabetes Association — eAG/A1C Conversion Calculator (DiabetesPro)
• National Glycohemoglobin Standardization Program (NGSP) — HbA1c and eAG
• American Diabetes Association — Standards of Care in Diabetes (diagnostic A1c thresholds)

The formula and category thresholds were last cross-checked against these sources on 2026-06-11. This tool is informational and does not provide medical advice or treatment targets — always confirm results with your doctor and an accredited lab.