Lab-formula accurate · updated for 2026
Read your A1C the way your clinic does.
Enter one number and get the other: your A1C percentage, your estimated average glucose, and exactly where that result sits on the diagnostic range — normal, prediabetes, or diabetes.
Typical lab reports range from 4.0% to 14.0%.
Diabetes range — talk with your care team about this result.
A1C reference range chart
Ranges as defined by the American Diabetes Association. Your clinician may interpret borderline results differently based on your full history.
| Category | A1C | 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 | 7.7 and above |
See the full A1C-to-glucose chart (4%–15%, mg/dL, mmol/L & IFCC)
What your A1C number actually means
A1C (also written HbA1c, glycated hemoglobin, or glycohemoglobin) is a blood test that reports the percentage of hemoglobin — the oxygen-carrying protein inside red blood cells — that has glucose permanently attached to it. Glucose in your bloodstream binds to hemoglobin continuously and irreversibly over the roughly 90–120 day lifespan of a red blood cell. Because that binding never reverses, the percentage measured on any given day is a running record of your average blood sugar exposure over the previous two to three months, weighted more heavily toward the most recent 30 days.
That's what separates A1C from a finger-stick or continuous glucose monitor (CGM) reading. A glucose meter tells you the truth about one moment. A1C tells you the truth about a season. Neither replaces the other — together they answer two different questions: "What is happening right now?" and "What has my body actually been living with, on average, for months?"
Who should have an A1C test, and how often
Testing recommendations differ depending on whether diabetes is already diagnosed:
- Adults without diabetes: the ADA recommends screening starting at age 35, or earlier if you're overweight and have an additional risk factor (family history, high blood pressure, a history of gestational diabetes, or belonging to a higher-risk population group). If results are normal, retesting every 3 years is typical.
- Prediabetes: annual retesting is generally advised, alongside a conversation about lifestyle changes that can lower future risk.
- Diagnosed diabetes, meeting treatment goals: most clinicians retest twice a year.
- Diagnosed diabetes, treatment recently changed or goals not met: testing every 3 months is standard, since that roughly matches how long it takes red blood cells to fully "turn over" and reflect a change in average glucose.
Reading your result on this page
Type a lab value into the calculator above and the gauge instantly shows where it sits relative to the three ADA diagnostic bands. A single result in the prediabetes or diabetes range is a prompt to talk with a clinician, not a diagnosis on its own — official diagnosis in a non-pregnant adult generally requires either two abnormal results, or one abnormal A1C confirmed by a second test method (such as fasting plasma glucose).
Enter your lab A1C or slide to explore values.
Read eAG in the units your meter already uses.
See the range instantly on the gauge, then confirm with your clinician.
Want the underlying math, or the full percentage-by-percentage table? Those live on their own pages so they can go into real depth without cluttering the calculator above.
The formula, explained
Where 28.7 and 46.7 come from, the ADAG study behind them, and why your meter average won't match exactly.
ReferenceFull conversion chart
Every A1C value from 4.0% to 15.0% mapped to mg/dL, mmol/L, and IFCC mmol/mol.
AnswersAll FAQs
Eighteen common questions on testing, accuracy, targets, and what affects your result.
Common questions
A short preview — the full FAQ page covers testing, accuracy, targets, and unit conversions in more depth.
A normal A1C is below 5.7%. Between 5.7% and 6.4% is classified as prediabetes. 6.5% or higher, confirmed on two separate tests, is classified as diabetes.
People without diabetes are typically screened every 1–3 years depending on risk factors. People managing diabetes are usually tested every 3–6 months, or more often if treatment recently changed.
A meter average is usually built from a handful of readings a day, which under-samples overnight and post-meal spikes. A1C reflects a continuous 24/7 average, so the two numbers are rarely identical even when both are correct.
No. This tool converts between units using a validated formula, but only a laboratory blood draw, interpreted by a clinician, can diagnose diabetes or prediabetes.
Medical disclaimer: This calculator is an educational tool based on the published ADAG conversion formula. It does not diagnose, treat, or replace advice from a qualified healthcare professional. Always confirm results with your clinician or lab.