A1C AND eAG CALCULATOR
Turn your A1C into a number you already understand.
Convert a laboratory A1C to estimated average glucose, estimate an A1C-like value from an average glucose, or switch glucose units in seconds.
CALCULATE
A1C and average glucose converter
Example: enter 5.7, not 0.057.
Use a true multi-day average, not one reading. For CGM data, also review the GMI reported by your system.
Converts concentration units only.
Estimated average glucose
117 mg/dL
Calculated from your A1C using the ADAG equation.
Educational use only. This calculator does not diagnose diabetes, set a personal target, or replace laboratory testing or medical care. Do not change medication based on this result.
THE SHORT ANSWER
What does your converted number mean?
A1C is the laboratory measure
It reports the percentage of hemoglobin with glucose attached and reflects roughly the past three months.
eAG is the translation
Estimated average glucose expresses that A1C in the same units used by a glucose meter or CGM.
Your daily readings will vary
An average can hide meal spikes, overnight patterns, lows, and the times you did not test.
COMPLETE GUIDE
A1C, estimated average glucose, and the story between the numbers
A1C is one of the most useful numbers in metabolic health, but it is also one of the easiest to misunderstand. It does not tell you what your glucose is right now. It does not reveal every rise and fall. It compresses months of changing glucose into one percentage.
01
What an A1C actually measures
Glucose circulates in your blood and attaches to hemoglobin, the oxygen-carrying protein inside red blood cells. The A1C test measures the percentage of hemoglobin that has glucose attached. Because red blood cells live for about three months, that percentage provides a longer view than a fasting glucose or a finger-stick reading.
A laboratory might report an A1C of 5.7%, 6.5%, or 8.0%. Those percentages can feel abstract. Estimated average glucose translates the percentage into the familiar units used by a meter or CGM. That is why an A1C of 7.0% can also be expressed as an estimated average glucose of about 154 mg/dL.
Why the last month matters more
People sometimes assume that A1C gives equal weight to every day in the prior three months. NIDDK explains that the most recent 30 days have a greater effect than the earlier part of the window. A meaningful recent change can therefore influence an A1C before a full 120-day red blood cell cycle has passed.
02
A1C to estimated average glucose chart
This chart uses the same ADAG relationship as the calculator. It is a conversion chart, not a personal target chart. Individual treatment goals depend on diagnosis, age, medications, pregnancy, other health conditions, and hypoglycemia risk.
| A1C | eAG mg/dL | eAG mmol/L | HbA1c mmol/mol |
|---|---|---|---|
| 4.0% | 68 | 3.8 | 20 |
| 4.5% | 82 | 4.6 | 26 |
| 5.0% | 97 | 5.4 | 31 |
| 5.5% | 111 | 6.2 | 37 |
| 5.7% | 117 | 6.5 | 39 |
| 6.0% | 126 | 7.0 | 42 |
| 6.4% | 137 | 7.6 | 46 |
| 6.5% | 140 | 7.8 | 48 |
| 7.0% | 154 | 8.6 | 53 |
| 7.5% | 169 | 9.4 | 58 |
| 8.0% | 183 | 10.1 | 64 |
| 8.5% | 197 | 10.9 | 69 |
| 9.0% | 212 | 11.8 | 75 |
| 10.0% | 240 | 13.4 | 86 |
| 11.0% | 269 | 14.9 | 97 |
| 12.0% | 298 | 16.5 | 108 |
Values are rounded. HbA1c mmol/mol is the IFCC reporting unit. It is not the same measurement as glucose mmol/L.
03
Four numbers that answer different questions
A1C
A percentage based on glycated hemoglobin. It reflects a weighted view of roughly three months.
eAG
An A1C-derived estimate expressed in mg/dL or mmol/L. It is not directly measured.
Meter reading
A glucose measurement at one moment, such as fasting, before a meal, or after eating.
CGM average and GMI
A sensor-derived average plus a separate CGM-specific estimate called Glucose Management Indicator.
A single fasting reading cannot tell you your A1C. A handful of carefully timed meter checks may not represent the full day. A CGM average covers many more moments, but its GMI can still differ from a laboratory A1C.
04
Why your meter, CGM, and A1C may not match
A mismatch is not automatically proof that one device or test is wrong. Each number comes from a different measurement method and may cover a different period.
If most finger sticks happen before breakfast, the average may miss post-meal rises, overnight changes, and higher readings on days you did not test.
A 14-day CGM average and a roughly three-month A1C do not summarize the same dates. Recent changes can widen the gap.
Two people can have the same average while one has a stable pattern and the other has larger highs and lows.
Red blood cell lifespan and hemoglobin differences can shift laboratory A1C relative to observed glucose.
Laboratory assays, glucose meters, and sensors each have expected variation. One isolated number deserves context.
When the numbers disagree, do not force them to tell the same story. Ask what each number measured.
05
The commonly used A1C reference ranges
For screening and diagnosis, the CDC and NIDDK list the following laboratory A1C ranges for nonpregnant adults. These are diagnostic reference ranges, not individualized treatment goals.
Normal reference range
Prediabetes reference range
Diabetes reference range
NIDDK states that, without clear symptoms, an A1C result in the diabetes or prediabetes range should be confirmed on a different day using A1C or another appropriate diabetes test.
06
When A1C can be misleading
A1C depends on both glucose exposure and red blood cells. Anything that changes red blood cell lifespan or interferes with the assay can affect the result. NIDDK and CDC identify several situations worth discussing with a clinician:
- Recent blood loss or blood transfusion
- Iron-deficiency anemia or other severe anemia
- Sickle cell disease, thalassemia, or certain hemoglobin variants
- Erythropoietin treatment or hemodialysis
- Kidney failure or advanced liver disease
- Early or late pregnancy
- A large mismatch between glucose patterns and A1C
This list is not complete, and the direction of the error is not always the same. A clinician can decide whether another assay method or a different glucose test is appropriate.
07
Questions to take to your next appointment
- Does my laboratory A1C fit the glucose pattern you see in my other tests?
- Could any health condition, medication, or blood disorder affect my A1C?
- Should this result be repeated or confirmed with another test?
- What target is appropriate for my history and current treatment?
- Which numbers should I track between now and the next visit?
WHY THIS TOOL EXISTS
One percentage can hide a dramatic change.
During my 2025 metabolic health crisis, my A1C was 7.2%. Thirty days later, it was 6.5%. Eight months after the first result, it was 5.7%. Those numbers were tracked with my physician while I was taking prescribed medication and making changes to my diet, activity, sleep, weight, and daily routine.
The percentage mattered, but translating it into average glucose made the size of the change easier to grasp. This calculator does not explain why my numbers changed and it cannot predict anyone else’s outcome. Its job is simpler: help you understand the units well enough to ask better questions.
08
Frequently asked questions
What is the difference between A1C and estimated average glucose?+
A1C is a laboratory percentage based on glycated hemoglobin. eAG is a mathematical translation of that percentage into mg/dL or mmol/L.
What formula does this calculator use?+
It uses the ADAG equation: eAG in mg/dL equals 28.7 times A1C minus 46.7.
What eAG corresponds to an A1C of 5.7%?+
An A1C of 5.7% corresponds to an estimated average glucose of about 117 mg/dL, or 6.5 mmol/L.
Why does my meter average not match my A1C-derived eAG?+
A meter average only includes the moments you tested. Time windows, test accuracy, red blood cell turnover, and individual biology can also contribute.
Can I calculate A1C from one glucose reading?+
No. One reading is a snapshot. The reverse calculator requires a representative multi-day average and still produces only an estimate.
Do I need to fast for an A1C test?+
No fasting is required for the A1C test itself. Other tests ordered at the same visit may require fasting.
How far back does an A1C look?+
A1C reflects roughly the previous three months, with the most recent 30 days influencing it more than the earlier part of the window.
Is eAG the same as a CGM average or GMI?+
No. eAG comes from laboratory A1C. A CGM average comes from sensor readings, and GMI uses a separate CGM-specific equation.
What can make an A1C result less reliable?+
Blood loss, transfusion, anemia, kidney or liver disease, pregnancy, altered red blood cell lifespan, and certain hemoglobin variants can affect accuracy.
Can this calculator diagnose prediabetes or diabetes?+
No. It cannot verify a test, consider your history, or make a diagnosis. Confirmation may require repeat or additional laboratory testing.
What is mmol/mol, and is it the same as mmol/L?+
No. mmol/mol is an IFCC unit for HbA1c. mmol/L is a concentration unit for glucose.
Can I use the result to change medication?+
No. Do not start, stop, or change medication based on this calculator.
KEEP CONNECTING THE NUMBERS
One result is useful. A connected pattern is clearer.
PRIMARY SOURCES
Research and official guidance
- American Diabetes Association: eAG/A1C Conversion Calculator
- NGSP: HbA1c and Estimated Average Glucose
- Nathan et al.: Translating the A1C Assay Into Estimated Average Glucose Values
- NIDDK: The A1C Test and Diabetes
- CDC: A1C Test for Diabetes and Prediabetes
- Bergenstal et al.: Glucose Management Indicator
Page researched and updated August 8, 2026. Educational content should be reviewed with a qualified healthcare professional before it is used to guide care.