Free a1c calculator
Turn your A1c into the everyday blood-sugar number you actually recognise. Enter your A1c and the calculator returns your estimated average glucose (eAG) in mg/dL and mmol/L, the ADA category it falls in, and a full A1c-to-blood-sugar conversion chart — or flip it to convert an average glucose reading back into an A1c — updated live, as you type.
On this page15 sections
| A1c | mg/dL | mmol/L | Category |
|---|---|---|---|
| 5.0% | 97 | 5.4 | Normal |
| 5.7% | 117 | 6.5 | Prediabetes |
| 6.0% | 126 | 7.0 | Prediabetes |
| 6.5% | 140 | 7.7 | Diabetes |
| 7.0% | 154 | 8.5 | Diabetes |
| 8.0% | 183 | 10.1 | Diabetes |
| 9.0% | 212 | 11.7 | Diabetes |
| 10.0% | 240 | 13.3 | Diabetes |
A1c conversion is informational, not a diagnosis. When A1c can be misleading
Results are estimates. Consult a professional.
What is A1c, and what does it measure?
A1c (also written HbA1c or glycated haemoglobin) is a blood test that reports the percentage of your haemoglobin — the oxygen-carrying protein in red blood cells — that has glucose stuck to it. The more glucose circulating in your blood, the more of it bonds to haemoglobin, a process called glycation. Because red blood cells live about three months, A1c reflects your average blood sugar over the past 2–3 months, not a single moment. That is exactly what this A1c calculator converts into an everyday glucose number.
A finger-stick or CGM reading tells you your glucose right now; A1c tells you the long-run trend. The two answer different questions — which is why a result from this calculator is an average, not the value you would see on a meter at any given time.
Because more recent red blood cells outnumber older ones, the most recent month weighs most heavily in the result — roughly half of an A1c reflects the prior 30 days, with the rest spread over the two months before that. That is why a change you make today does not fully show up in your A1c for two to three months, and why A1c is the standard tool for confirming a diabetes diagnosis and tracking long-term control rather than day-to-day adjustments.
How the A1c to average blood sugar calculator works
The calculator turns your A1c percentage into an estimated average glucose (eAG) — your A1c expressed in the same mg/dL or mmol/L units your home meter and CGM use. It uses the formula the American Diabetes Association adopted from the landmark ADAG study, which mapped thousands of glucose readings against measured A1c across hundreds of participants.
Enter the value you have. Type an A1c to get your average glucose, or — using the toggle in the calculator — type an average glucose (in mg/dL or mmol/L) to get the A1c it implies. Each direction uses the matching coefficients, so the conversion is exact either way.
A worked example using the A1c calculator
David's lab report comes back with an A1c of 7.0%. He wants to know what that means in the mg/dL numbers he sees on his meter. Here is the arithmetic the calculator runs.
Step 1 — Multiply the A1c by 28.7
Take the A1c and multiply: 28.7 × 7.0 = 200.9.
Step 2 — Subtract 46.7
200.9 − 46.7 = 154.2 mg/dL. The mmol/L cross-check (1.59 × 7.0 − 2.59) gives 8.5 mmol/L — the same average expressed in the other common unit.
Step 3 — Read the category and target
An A1c of 7.0% sits in the diabetes range (6.5% and above) — and is also the standard ADA target for most non-pregnant adults with diabetes. So David is right at his goal.
A1c to average blood sugar conversion chart
Most people want the whole picture, not just their own number. The table below runs the ADA formula across the common A1c range, in both mg/dL and mmol/L. Find your A1c on the left and read across — this is the reference chart competitors usually split across two pages.
| A1c (%) | eAG (mg/dL) | eAG (mmol/L) | Category |
|---|---|---|---|
| 5.0 | 97 | 5.4 | Normal |
| 5.6 | 114 | 6.3 | Normal |
| 5.7 | 117 | 6.5 | Prediabetes |
| 6.0 | 126 | 7.0 | Prediabetes |
| 6.4 | 137 | 7.6 | Prediabetes |
| 6.5 | 140 | 7.7 | Diabetes |
| 7.0 | 154 | 8.5 | Diabetes |
| 7.5 | 169 | 9.3 | Diabetes |
| 8.0 | 183 | 10.1 | Diabetes |
| 9.0 | 212 | 11.7 | Diabetes |
| 10.0 | 240 | 13.3 | Diabetes |
| 11.0 | 269 | 14.9 | Diabetes |
| 12.0 | 298 | 16.5 | Diabetes |
eAG computed from the ADA/ADAG formulas (28.7 × A1c − 46.7 for mg/dL; 1.59 × A1c − 2.59 for mmol/L), rounded. Categories use ADA diagnostic cut-offs.
A1c levels: normal, prediabetes, and diabetes ranges
The American Diabetes Association sorts A1c into three diagnostic bands. A diagnosis of prediabetes or diabetes is normally confirmed with a repeat test, but these cut-offs are the standard starting point.
| Category | A1c range | Roughly (eAG mg/dL) |
|---|---|---|
| Normal | below 5.7% | under ~117 |
| Prediabetes | 5.7% – 6.4% | ~117 – 137 |
| Diabetes | 6.5% and above | ~140 and up |
Source: American Diabetes Association, Standards of Care in Diabetes — diagnostic A1c criteria.
What is a good A1c target?
For most non-pregnant adults with diabetes, the ADA's general target is an A1c below 7.0% (an eAG under about 154 mg/dL / 8.5 mmol/L). But there is no single right number — targets are individualised.
- A1c < 7.0% — the standard goal for many adults with diabetes, balancing benefit against the risk of low blood sugar.
- A1c < 6.5% — a tighter goal sometimes used for younger people or those early in their diabetes, if it can be reached safely.
- A1c < 8.0% — a looser, safer goal for older adults, people with a limited life expectancy, or anyone prone to severe hypoglycaemia.
Your own target is a conversation with your clinician — age, how long you have had diabetes, other health conditions, and your risk of low blood sugar all move the line. Use the number from this calculator to track your trend, not to set your goal alone.
It is also worth knowing that lower is not always better. Driving A1c down too aggressively — especially on insulin or sulfonylureas — raises the risk of hypoglycaemia (dangerously low blood sugar), which is why guidelines pair every A1c goal with a hypoglycaemia-risk check. For people without diabetes, an A1c that stays under 5.7% is the simple goal; for those with prediabetes, pulling it back below 5.7% through diet, activity, and weight loss can return it to the normal range.
Why your eAG differs from your meter average
A frequent surprise: the average glucose this calculator gives from your A1c is often higher than the average of the readings on your meter. That does not mean either number is wrong — they measure different things.
Most people check their meter when it is convenient — fasting in the morning or before meals — and those are usually the lowest points of the day. eAG, by contrast, reflects glucose around the clock, including the after-meal peaks most people never test. So the meter average skews low while eAG captures the true 24-hour picture. A continuous glucose monitor, which samples all day, lands much closer to eAG.
There is a second reason the two can diverge: the A1c-to-eAG relationship is an average across many people, and individuals vary. Some people consistently run a little higher or lower than the formula predicts for their A1c — so treat eAG as a well-grounded estimate of your average, not a guaranteed exact match to your own glucose pattern.
When A1c can be misleading
A1c is reliable for most people, but because it depends on red blood cells and their lifespan, anything that changes those cells can throw the result off — making it read falsely high or falsely low even when your actual glucose has not changed.
Causes of a falsely low A1c
Conditions that shorten red-cell lifespan or boost cell turnover lower A1c: recent blood loss or transfusion, haemolytic anaemia, sickle cell or other haemoglobin traits, chronic kidney disease (especially with erythropoietin treatment), and pregnancy. In these cases the A1c can look better than your day-to-day glucose really is.
Causes of a falsely high A1c
Iron-deficiency anaemia, vitamin B12 deficiency, and some other conditions extend red-cell lifespan or otherwise raise A1c, so it can read worse than your true average.
Haemoglobin variants
Inherited haemoglobin variants (such as HbS, HbC, HbE, and thalassaemia traits) can interfere with certain A1c assays. People affected may need a variant-tolerant test method or an alternative measure such as fructosamine or CGM-based time in range.
How to lower your A1c
Because A1c is an average of the last few months, it moves slowly — give any change about 8–12 weeks to show up. The levers are the familiar ones, and small, consistent changes add up:
- Flatten post-meal spikes. The after-meal highs that meters miss are what drive A1c up. Smaller portions of refined carbs, more fibre and protein, and a short walk after eating all blunt the peak.
- Move most days. Regular activity improves insulin sensitivity, so the same food raises glucose less. Even brief, frequent movement helps.
- Take medication as prescribed. If you are on glucose-lowering medication or insulin, consistency matters more than any single dose — missed doses show up in the average.
- Lose a modest amount of weight if you carry excess. For many people with type 2 diabetes, a 5–10% weight loss meaningfully lowers A1c.
It helps to know roughly how much each step moves the number. As a rough guide, every 28.7 mg/dL you shave off your average glucose lowers your A1c by about one percentage point — so trimming a daily average from 183 mg/dL to 154 mg/dL is the difference between an 8.0% and a 7.0% result. That is why consistency beats intensity: holding a slightly lower average every day moves A1c more reliably than occasional perfect days surrounded by spikes.
Re-test on the schedule your clinician sets — typically every 3–6 months — and watch the trend rather than chasing each reading. Pair this calculator with the BMI calculator to track weight alongside your A1c.
Data sources and methodology
The A1c-to-eAG conversion uses the formulas from the A1c-Derived Average Glucose (ADAG) study (Nathan DM et al., Diabetes Care, 2008), which the American Diabetes Association adopted for estimated average glucose reporting. Diagnostic categories (normal < 5.7%, prediabetes 5.7–6.4%, diabetes ≥ 6.5%) and the < 7.0% general target follow the ADA's Standards of Care in Diabetes. Conversions are computed exactly and rounded for display.
American Diabetes Association — eAG/A1c conversion and Standards of Care; ADAG study (Nathan et al., 2008).Frequently asked questions about the free a1c calculator
About this A1c calculator
This A1c calculator runs entirely in your browser. The value you type never leaves your device — nothing is sent to a server, logged, or shared. It converts A1c to estimated average glucose with the ADA's ADAG-study formula (28.7 × A1c − 46.7 for mg/dL), classifies the result against the ADA diagnostic bands, and updates instantly on every change.
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