HbA1c (glycated hemoglobin) measures the percentage of hemoglobin proteins in your blood that have glucose attached. Since red blood cells live about 3 months, HbA1c reflects your average blood sugar over that period. It's a more stable metric than a single glucose reading.

What HbA1c level is considered normal?

Below 5.7% is normal. Between 5.7% and 6.4% indicates prediabetes. 6.5% or higher on two separate tests is used for diabetes diagnosis. Personal treatment targets may differ from those diagnostic cutoffs.

Is the ADAG formula accurate?

The ADAG formula (Nathan et al., 2008) was derived from a study of 507 participants using continuous glucose monitors. The correlation between A1c and average glucose was r = 0.92. It's considered the best available conversion, though individual variation exists.

Why might my A1c not match my glucose meter readings?

Several factors cause discordance: testing frequency and timing (you may miss highs/lows), hemoglobin variants (HbS, HbC), iron deficiency anemia, kidney disease, or pregnancy. If your A1c seems inconsistent with your meter data, discuss alternative monitoring with your provider.

How quickly can I change my HbA1c?

Because A1c reflects a 2–3 month average, it takes about that long to see meaningful changes. The most recent 30 days have the greatest influence. Significant dietary and medication changes can shift A1c by 0.5–1.0% in a quarter.

What does each 1% change in A1c mean?

Each 1% change in HbA1c corresponds to roughly 29 mg/dL (1.6 mmol/L) change in estimated average glucose. That translation is useful for understanding the scale of the difference, but the clinical meaning depends on the broader diabetes context.

HbA1c to Average Glucose Calculator

Convert HbA1c percentage to estimated average glucose (eAG) in mg/dL and mmol/L using the ADAG study formula. Classify your A1c level.

⚠️ Medical Disclaimer: This calculator is for educational purposes only. It does not provide medical advice or diagnosis. Consult your healthcare provider for interpretation of HbA1c results.

HbA1c (%)

HbA1c 6%

eAG (mg/dL)

125

eAG (mmol/L)

Prediabetes

eAG (mg/dL)

125

Estimated average glucose

eAG (mmol/L)

Estimated average glucose

HbA1c

Prediabetes

A1c Classification

4%5.76.57.08.012%

Normal: < 5.7%

Prediabetes: 5.7–6.4%

Diabetes: ≥ 6.5%

Target: < 7.0%

HbA1c to eAG Reference Table

HbA1c (%)	eAG (mg/dL)	eAG (mmol/L)	Classification
4.0	68	3.8	Normal
4.5	82	4.6	Normal
5.0	97	5.4	Normal
5.5	111	6.2	Normal
5.7	117	6.5	Prediabetes
6.0	125	7	Prediabetes
6.4	137	7.6	Prediabetes
6.5	140	7.8	Diabetes (At Target)
7.0	154	8.6	Diabetes (Above Target)
7.5	169	9.4	Diabetes (Above Target)
8.0	183	10.2	Diabetes (High Risk)
8.5	197	11	Diabetes (High Risk)
9.0	212	11.8	Diabetes (High Risk)
9.5	226	12.6	Diabetes (High Risk)
10.0	240	13.3	Diabetes (High Risk)
11.0	269	14.9	Diabetes (High Risk)
12.0	298	16.5	Diabetes (High Risk)

Planning notes, formulas, and examples

About the HbA1c to Average Glucose Calculator

This calculator converts HbA1c to estimated average glucose (eAG) using the ADAG study equation. It reports the result in both mg/dL and mmol/L so a lab A1c value can be compared more easily with everyday glucose-meter units.

The page also shows the common ADA threshold bands for normal, prediabetes, and diabetes. That makes it useful for translating an A1c result into more familiar glucose terms, while still keeping the interpretation at a broad educational level.

When This Page Helps

A1c and fingerstick glucose use different units and different time horizons. Converting A1c to eAG gives a quick bridge between lab results and meter-style numbers without doing the ADAG math manually.

How to Use the Inputs

Enter your HbA1c percentage from your lab report.
View the estimated average glucose (eAG) in both mg/dL and mmol/L.
See your A1c classification (normal, prediabetic, diabetic).
Review the A1c-to-glucose reference table.
Discuss your results with your healthcare provider.

Formula used

ADAG Study Formula (Nathan et al., 2008):
eAG (mg/dL) = 28.7 × HbA1c − 46.7
eAG (mmol/L) = 1.5944 × HbA1c − 2.5944

A1c Classification (ADA):
• Normal: < 5.7%
• Prediabetes: 5.7–6.4%
• Diabetes: ≥ 6.5%

Target for most diabetics: < 7.0% (eAG ~154 mg/dL)

Example Calculation

Result: eAG = 154 mg/dL (8.6 mmol/L) — Diabetes range

eAG = 28.7 × 7.0 − 46.7 = 200.9 − 46.7 = 154.2 mg/dL. The page labels 7.0% in the diabetes range and translates it into a meter-style average glucose value. Personal glucose targets still depend on the broader diabetes plan rather than on this conversion alone.

Tips & Best Practices

HbA1c is usually followed over time rather than interpreted from one isolated result.
Conditions like anemia, hemoglobin variants, and recent blood loss can falsely alter HbA1c results.
A1c reflects a weighted average — the most recent month contributes ~50% of the result.
Estimated average glucose is a translation aid; it does not replace daily readings or CGM trends.
Some people have "discordant" A1c — their A1c doesn't match their glucose meter average. Discuss with your doctor.
Continuous glucose monitors (CGMs) now provide Time in Range (TIR), which complements A1c.

The ADAG Conversion

The A1c-Derived Average Glucose (ADAG) study established the modern formula for translating HbA1c into estimated average glucose. That is what this page does: it turns a lab percentage into a meter-style number in mg/dL and mmol/L so the result is easier to compare with everyday glucose readings.

Why the Translation Can Drift

A1c and meter averages do not always line up perfectly. Anemia, altered red-cell lifespan, kidney disease, hemoglobin variants, pregnancy, and recent transfusion can all make the A1c-to-eAG translation less reliable.

Use It as a Translation Tool

This page is best used to convert between HbA1c and average glucose language. It is not a medication-target engine and it does not replace individual goals set from meter data, CGM trends, or the broader diabetes workup.

Sources & Methodology

Last updated: March 27, 2026

Methodology

This page converts HbA1c to estimated average glucose using the ADAG equation, then reports the result in both mg/dL and mmol/L. It also maps the entered HbA1c value to broad ADA threshold bands for normal, prediabetes, and diabetes classification.

The result is a translation tool, not a replacement for individualized diabetes management. HbA1c can be misleading in some settings, including anemia, hemoglobin variants, kidney disease, pregnancy, or recent blood loss, so the output should be read with the broader clinical picture.

Sources

Translating the A1C assay into estimated average glucose values (Diabetes Care) — Original ADAG study publication.
Standards of Care in Diabetes (American Diabetes Association)

Frequently Asked Questions

HbA1c (glycated hemoglobin) measures the percentage of hemoglobin proteins in your blood that have glucose attached. Since red blood cells live about 3 months, HbA1c reflects your average blood sugar over that period. It's a more stable metric than a single glucose reading.