Estimated Average Glucose Calculator — eAG from HbA1c
Enter your HbA1c percentage to see your estimated average glucose (eAG) — the average blood sugar over the past 2–3 months — expressed in the same mg/dL or mmol/L units used on a home glucose meter.
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Display eAG in
HbA1c 7 % — Category: Diabetes range (ADA 2023)
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Scale HbA1c
28.7 × 7 = 200.9 - 2
Estimated average glucose
200.9 − 46.7 = 154.2Nathan 2008 linear regression (mg/dL).
How does this calculator work?
eAG (mg/dL) = 28.7 × HbA1c(%) − 46.7 (equivalently mmol/L = 1.594 × HbA1c − 2.594). Derived from the ADAG study (Nathan 2008, Diabetes Care). HbA1c 7% ≈ eAG 154 mg/dL; 6.5% (diabetes threshold) ≈ 140 mg/dL; 5.7% (prediabetes) ≈ 117 mg/dL. Accuracy is ±14 mg/dL (1 SD).
Formula
How this is calculated
Glycated haemoglobin (HbA1c) reflects the proportion of haemoglobin molecules that have been irreversibly glycated by glucose over the ~120-day life of a red blood cell. Because it integrates blood glucose over time, HbA1c is the standard long-term marker for glycaemic control in diabetes management. However, its percentage units are not intuitive for patients who measure blood glucose daily.
The estimated average glucose (eAG) translates HbA1c into the more familiar mg/dL or mmol/L units by applying linear regression equations derived from the ADAG (A1c-Derived Average Glucose) study — Nathan DM et al., Diabetes Care 2008. That study measured continuous glucose in 507 patients across multiple types and stages of diabetes and found a strong linear relationship between HbA1c and average glucose: eAG (mg/dL) = 28.7 × HbA1c − 46.7 (r² = 0.84). The conversion has a standard error of about ±14 mg/dL (±0.8 mmol/L) at typical HbA1c values.
For context, the ADA 2023 guidelines classify HbA1c below 5.7% as normal, 5.7–6.4% as prediabetes, and 6.5% or above as diabetes. An HbA1c of 7.0% corresponds to an eAG of about 154 mg/dL (8.6 mmol/L) — the typical treatment target for many adults with diabetes. The equation is valid for the NGSP/IFCC percentage scale (not IFCC mmol/mol units); if your result is in mmol/mol, divide by 10.929 to convert to %.
Frequently asked questions
HbA1c reflects average glucose over 2–3 months, weighted toward more recent weeks. Daily meters capture only specific moments — fasting, post-meal, or random — which may be systematically lower or higher than the true 24-hour average. The eAG is an average of all readings including post-meal peaks; so if you mainly test fasting, your meter readings will usually be lower than the eAG.
No. A fasting glucose test measures your blood sugar at a single point after at least 8 hours of fasting. eAG is a derived 2–3 month average that includes both fasting and post-meal levels. eAG will typically be higher than fasting glucose because it incorporates post-prandial peaks. A fasting level of 100 mg/dL with good meal-time control could correspond to an eAG of 130–140 mg/dL depending on your post-meal rises.
The ADAG regression applies to most adults but has known inaccuracies in people with conditions that shorten red-blood-cell lifespan (haemolytic anaemia, sickle-cell trait, recent blood transfusion) — these cause falsely low HbA1c relative to actual average glucose. In contrast, iron-deficiency anaemia can falsely elevate HbA1c. For patients with these conditions, continuous glucose monitoring (CGM) provides more reliable time-in-range estimates.
Also known as
TG we-Calculate Editorial Team. (2026). Estimated Average Glucose Calculator — eAG from HbA1c [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/estimated-average-glucose-calculator
TG we-Calculate Editorial Team. "Estimated Average Glucose Calculator — eAG from HbA1c." TG we-Calculate. 2026. https://we-calculate.com/calculator/estimated-average-glucose-calculator.
TG we-Calculate Editorial Team, "Estimated Average Glucose Calculator — eAG from HbA1c," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/estimated-average-glucose-calculator
@misc{wecalculate_estimated_average_glucose_calculator, title = {Estimated Average Glucose Calculator — eAG from HbA1c}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/estimated-average-glucose-calculator}}, year = {2026}, note = {TG we-Calculate} }
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