eAG Calculator

Convert your HbA1c into estimated average glucose (eAG), the same mg/dL or mmol/L units shown on a home glucose meter, using the ADAG study formula. This makes your A1c easier to relate to your day-to-day readings. For full bidirectional unit conversion, see the linked HbA1c converter. Informational reference, not a diagnostic test.

HbA1c

% (NGSP)

Estimated Average Glucose (eAG)

eAG is a population-average estimate. Your personal average glucose may differ by roughly ±15–20 mg/dL because glycation rates and red-cell lifespan vary between people. Need to convert HbA1c between % and mmol/mol too? Use the HbA1c to Average Glucose Converter.

Tracking your HbA1c? See your glucose trend over time and get personalized ranges in the Health3 app.

What eAG Is

Estimated average glucose (eAG) translates your HbA1c, a percentage, into the everyday glucose units you see on a meter or continuous glucose monitor: mg/dL or mmol/L. The point is intuition. An HbA1c of "7.0%" is abstract; an eAG of "154 mg/dL" or "8.6 mmol/L" connects directly to the numbers you check at home.

The conversion comes from the A1c-Derived Average Glucose (ADAG) study (Nathan et al., 2008, Diabetes Care 31:1473–1478), which used continuous glucose monitoring and frequent fingerstick readings in 507 people across 10 international centres to fit a linear relationship between HbA1c and average glucose.

ADAG formulas (Nathan et al., 2008):
eAG (mg/dL) = 28.7 × HbA1c% − 46.7
eAG (mmol/L) = 1.59 × HbA1c% − 2.59

HbA1c and ADA Diagnostic Categories

The table pairs HbA1c with its eAG and the American Diabetes Association diagnostic categories. These are published reference thresholds; a single abnormal result is usually confirmed before any clinical diagnosis.

Category (ADA)	HbA1c %	eAG mg/dL	eAG mmol/L
Normal	Below 5.7	Below 117	Below 6.5
Prediabetes	5.7 – 6.4	117 – 137	6.5 – 7.6
Diabetes	6.5 and above	140 and above	7.8 and above

Why Your Real Average May Differ

Individual variation. eAG is a population average; your personal value can differ by about ±15–20 mg/dL because glycation rates and red-cell lifespan vary.
Conditions that affect red cells. Anaemia, haemoglobinopathies, recent transfusion, chronic kidney disease, and pregnancy can make HbA1c (and therefore eAG) an unreliable mirror of true average glucose.
GMI is different. The Glucose Management Indicator from a CGM uses a different equation and often differs from lab HbA1c in the same person.

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Frequently Asked Questions

What is eAG (estimated average glucose)?

eAG translates your HbA1c into the mg/dL or mmol/L units shown on a glucose meter, so your A1c is easier to relate to daily readings. The formula comes from the ADAG study (Nathan et al., Diabetes Care 2008): eAG (mg/dL) = 28.7 x HbA1c% - 46.7, and eAG (mmol/L) = 1.59 x HbA1c% - 2.59.

Is eAG the same as my actual average glucose?

Not exactly. eAG is a population-average estimate, so your real average can differ by roughly plus or minus 15 to 20 mg/dL because glycation rates and red-cell lifespan vary between people. It is a useful translation of HbA1c, not a measurement of your specific average.

How is eAG different from the GMI on my CGM?

The Glucose Management Indicator (GMI) is calculated from continuous glucose monitor data using a different equation, while eAG is derived from HbA1c. The two often differ by 0.5% or more in the same person because they measure related but distinct things. Neither is simply more accurate.

Do I need this if I have the HbA1c converter?

This tool focuses specifically on turning HbA1c into average glucose. If you also need to convert HbA1c between % (NGSP) and mmol/mol (IFCC), or start from an eAG value, use the HbA1c to Average Glucose Converter, which handles all four values at once.

What HbA1c corresponds to a normal average glucose?

An HbA1c below 5.7% is the ADA normal category, corresponding to an eAG below about 117 mg/dL (6.5 mmol/L). Prediabetes is 5.7 to 6.4% and diabetes is 6.5% or higher. These are published diagnostic thresholds, and a single result is usually confirmed before any clinical diagnosis.

Medical Disclaimer: eAG is a statistical estimate from the ADAG study (Nathan DM, et al. Diabetes Care. 2008;31(8):1473–1478) and may differ from your true average glucose by about ±15–20 mg/dL. HbA1c can be unreliable in anaemia, haemoglobinopathies, recent transfusion, chronic kidney disease, and pregnancy. The ADA categories shown are published thresholds, not a diagnosis. This tool is for informational and educational use only. Always consult a qualified healthcare provider to interpret your results.

Track Your HbA1c and Glucose Over Time

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