Estimated Average Glucose (eAG) Calculator
Enter your HbA1c percentage to get your estimated average glucose (eAG) in both mg/dL and mmol/L. Or flip the mode and enter a blood glucose reading to find the matching HbA1c. The result includes a clinical interpretation, the ADA target range, and a full conversion chart showing how every HbA1c from 5% to 14% maps to a daily glucose level.
Formula
Worked example
An HbA1c of 7.0%: eAG = (28.7 x 7.0) - 46.7 = 200.9 - 46.7 = 154.2 mg/dL. In mmol/L: 154.2 / 18.0182 = 8.56 mmol/L. This equals the ADA general glycaemic target for most adults with diabetes.
What is estimated average glucose (eAG)?
Estimated average glucose (eAG) is a plain-language translation of your HbA1c laboratory result into the same milligrams-per-decilitre (mg/dL) or millimoles-per-litre (mmol/L) units shown on your glucose meter. HbA1c measures the percentage of haemoglobin molecules that have glucose attached to them, reflecting roughly the past 90 days of blood sugar control. Because HbA1c is a percentage rather than a glucose reading, many patients find it abstract. The American Diabetes Association (ADA) and the European Association for the Study of Diabetes (EASD) jointly endorsed eAG in 2008 as a way to bridge that gap, allowing clinicians and patients to discuss targets in familiar glucose units.
The ADAG formula and where it comes from
The conversion formula, eAG (mg/dL) = 28.7 x HbA1c (%) - 46.7, comes from the A1c-Derived Average Glucose (ADAG) study published by Nathan and colleagues in Diabetes Care (2008). The study enrolled 507 people from four continents who wore continuous glucose monitors for three months while also having regular HbA1c measurements taken. The linear regression of those paired data produced the formula above. The 95% confidence interval of the relationship means your actual average glucose could be roughly 15-20 mg/dL higher or lower than the eAG for a given HbA1c. eAG is therefore an estimate, not an exact reading. To convert mg/dL to mmol/L, divide by 18.0182 (the molar mass ratio of glucose).
ADA clinical targets and diagnostic cut-offs
The ADA uses HbA1c at three key thresholds: below 5.7% is normal, 5.7-6.4% is prediabetes, and 6.5% or above is a diagnostic criterion for diabetes (when confirmed by a second test). For people already diagnosed with diabetes, the ADA recommends an HbA1c below 7.0% (eAG below about 154 mg/dL / 8.6 mmol/L) for most non-pregnant adults, as this target balances glycaemic benefit against hypoglycaemia risk. Tighter control (below 6.5% / eAG below 140 mg/dL) may suit younger patients with a short disease duration and no cardiovascular disease. A higher target (below 8.0% / eAG below 183 mg/dL) is often appropriate for older adults, people with frequent hypoglycaemia, or those with limited life expectancy. Pregnant women with pre-existing diabetes are typically advised to aim for below 6.0% (eAG below 126 mg/dL) if this can be achieved without significant hypoglycaemia.
Why eAG differs from your fasting glucose or meter average
Your fasting glucose reading reflects only the moment the blood was drawn, usually after an overnight fast. Meter averages cover only the times you test, which may miss post-meal spikes or overnight lows. HbA1c, and therefore eAG, is influenced by the entire 24-hour glucose profile over approximately three months, weighted towards the most recent weeks because red blood cells are continuously replaced. This is why HbA1c can be elevated even when fasting readings look reasonable: it captures the glucose excursions that occur after meals and during the night that spot checks miss. Conversely, HbA1c can appear falsely low in people with haemolytic anaemia, iron-deficiency anaemia, or haemoglobin variants such as HbS or HbC, because those conditions alter red-blood-cell turnover. In those cases, alternative markers such as fructosamine or glycated albumin may be used instead.
HbA1c to eAG conversion chart
| HbA1c (%) | eAG (mg/dL) | eAG (mmol/L) | Variability range (mg/dL) | ADA category |
|---|---|---|---|---|
| 5 | 97 | 5.4 | 76-120 | Normal |
| 5.5 | 111 | 6.2 | 88-137 | Normal |
| 5.7 | 117 | 6.5 | 93-143 | Prediabetes threshold |
| 6 | 126 | 7 | 100-152 | Prediabetes |
| 6.4 | 137 | 7.6 | 110-164 | Prediabetes upper limit |
| 6.5 | 140 | 7.8 | 113-167 | Diabetes threshold |
| 7 | 154 | 8.6 | 123-185 | ADA general target |
| 7.5 | 169 | 9.4 | 135-205 | Above ADA target |
| 8 | 183 | 10.2 | 147-217 | Above ADA target |
| 8.5 | 197 | 10.9 | 159-231 | Above ADA target |
| 9 | 212 | 11.8 | 170-249 | High |
| 10 | 240 | 13.4 | 193-282 | High |
| 11 | 269 | 14.9 | 217-314 | Very high |
| 12 | 298 | 16.5 | 240-347 | Very high |
| 14 | 355 | 19.7 | 288-414 | Very high |
ADAG formula (Nathan 2008). Variability range shows the 95% confidence interval from the study population.
Frequently asked questions
What is a good eAG level?
For most adults with diabetes, an eAG below 154 mg/dL (8.6 mmol/L), which corresponds to an HbA1c below 7.0%, is the ADA general target. For people without diabetes, an eAG below 117 mg/dL (6.5 mmol/L) is considered normal. For pregnant women with diabetes, the target is typically an eAG below 126 mg/dL (7.0 mmol/L), corresponding to HbA1c below 6.0%. Your personal target should be set by your healthcare team based on your individual situation.
How accurate is the eAG conversion from HbA1c?
The ADAG formula has a 95% confidence interval of about plus or minus 15-20 mg/dL, meaning your true average glucose could reasonably differ from the eAG by that amount. The formula was derived from a diverse population, but individual variation in HbA1c measurement, haemoglobin variants, and red-blood-cell lifespan can all cause the eAG to differ from a person's measured mean glucose. Treat eAG as a useful estimate for conversations, not a precise glucose reading.
How is eAG different from my meter average?
Your meter average covers only the moments you tested, which are often clustered around meals and miss the full overnight and post-meal picture. HbA1c (and therefore eAG) reflects an integrated average of your glucose across roughly the past three months, around the clock, because it is set by how much glucose attaches to haemoglobin over the red blood cell lifespan. So eAG tends to be higher than a selective meter average if you test mainly when your glucose is at its best.
Can I use this calculator if my meter reads in mmol/L?
Yes. Switch the mode to "eAG to HbA1c" and select mmol/L as your unit. Enter your average glucose in mmol/L and the calculator converts it to mg/dL internally, then uses the ADAG formula to estimate your HbA1c. The mg/dL equivalent is also shown so you can compare with US-format resources.
Why might my HbA1c not match the eAG formula?
Several conditions can cause HbA1c to be falsely high or low independent of actual glucose levels. Haemolytic anaemia and iron-deficiency anaemia alter red-blood-cell turnover and lower or raise HbA1c, respectively. Haemoglobin variants (HbS, HbC, HbE) interfere with some assay methods. Recent blood transfusions introduce donor haemoglobin and can lower HbA1c. In these situations, fructosamine, glycated albumin, or continuous glucose monitor data may give a more reliable picture.
How often is HbA1c tested and does that affect eAG?
The ADA recommends testing HbA1c at least twice a year if glucose is stable and at target, or every three months when changing therapy or when not at goal. Because eAG is derived directly from a single HbA1c value, it reflects that particular snapshot and changes each time you are re-tested. Continuous glucose monitors report a related metric called the glucose management indicator (GMI), calculated from mean sensor glucose, which can differ from HbA1c-derived eAG by about 0.3 percentage points on average.