A1C to Glucose Calculator
Convert A1C to estimated average glucose and back, in mg/dL, mmol/L and IFCC units.
Your result
A1C is unreliable in anaemia, sickle cell trait and other haemoglobin variants, in pregnancy, in kidney or liver disease, and after a recent transfusion, in all of those the number can be badly wrong in either direction. Diagnosis needs two abnormal tests or one plus symptoms, interpreted by a doctor.
This converts between A1C percentage and estimated average glucose, in both mg/dL and mmol/L.
It shows which diagnostic band the result falls in, and it is not a substitute for medical advice.
What A1C measures
A1C, or HbA1c, measures the percentage of your haemoglobin that has glucose attached to it. Because red blood cells live around three months, it reflects your average blood glucose over roughly the last two to three months rather than a single moment.
That is what makes it useful. A finger-prick reading tells you about this minute; A1C tells you about the season. It cannot be improved by fasting the night before a test.
The estimated average glucose conversion translates the percentage into the units a home meter uses. An A1C of 7% is an average of about 154 mg/dL, and 6.5% is about 140 mg/dL.
Each 1% of A1C is about 28.7 mg/dL of average glucose. The relationship is linear across the usual range.
What to enter
- A1C percentage
- From a lab result or a point-of-care test. Converts to an estimated average glucose.
- Average glucose
- The reverse direction. Enter an average from meter or CGM readings to estimate the A1C it corresponds to.
- Units
- mg/dL is standard in the US; mmol/L is used in most other countries. Divide mg/dL by 18 to convert.
Diagnostic bands for adults
- Below 5.7%
- Normal. About 117 mg/dL and below.
- 5.7% to 6.4%
- Prediabetes. Often reversible with diet, weight loss and activity.
- 6.5% and above
- Diabetes range, when confirmed by a repeat test or a second test type.
- Treatment targets
- Individual, and set with your clinician. They vary with age, other conditions and hypoglycaemia risk.
What this assumes
The eAG conversion comes from the ADAG study and is a population average. Individual glycation rates vary, so two people with the same A1C can have somewhat different average glucose.
Conditions affecting red blood cell lifespan (anaemia, haemoglobin variants, recent transfusion, pregnancy, kidney disease) can make A1C unreliable.
How to calculate your A1C and average glucose
A single linear relationship converts between the two, in either direction.
- A1C
- As a percentage, so 7 rather than 0.07
- eAG
- Estimated average glucose. Divide by 18 for mmol/L
Take the A1C percentage. From a lab report. Enter it as a plain number, so 7 rather than 0.07.
Apply the conversion. 28.7 × 7 − 46.7 = 154 mg/dL.
Convert units if needed. Divide by 18 for mmol/L, so 154 mg/dL is about 8.6 mmol/L.
Reverse it to check against your meter. Add 46.7 and divide by 28.7. If your meter average and your A1C disagree substantially, that is worth raising with your doctor.
See a worked example: reading a lab result in meter units
- A1C
- 7.0%
eAG: 28.7 × 7.0 − 46.7 = 154 mg/dL, which is about 8.6 mmol/L.
For context, 6.5% is 140 mg/dL and 5.7% is 117 mg/dL.
So moving from 8.0% to 7.0% means dropping average glucose from 183 to 154, about 29 mg/dL.
Because A1C covers two to three months, a change made this week will not show fully until the next test.
7.0% is about 154 mg/dL
Frequently asked questions
The percentage of haemoglobin with glucose attached. Red blood cells live about three months, so it reflects your average glucose over roughly two to three months.
That is why it complements daily readings rather than replacing them. A meter shows a moment; A1C shows the underlying pattern.
Below 5.7% is normal. 5.7% to 6.4% is prediabetes. 6.5% and above indicates diabetes, when confirmed by a repeat or a second test type.
Treatment targets for someone already diagnosed are individual and set with a clinician. They depend on age, other conditions and how much hypoglycaemia risk is acceptable.
Not meaningfully. It reflects two to three months of glucose, so a few days of careful eating will barely move it.
The most recent month does weigh more heavily than earlier ones, so recent improvement shows up more. But sustained change over months is the only thing that shifts it substantially.
The eAG conversion is a population average, and individual glycation rates genuinely differ. Two people with identical average glucose can have A1C readings a few tenths apart.
Meter averages can also be biased by when you test. Checking mostly before meals misses post-meal peaks, which pushes the average low while the A1C sees everything.
Commonly every three months when glucose is not at target or treatment has changed, and every six months when stable.
Testing more often than about every three months adds little, since the measure reflects that whole period. Your clinician sets the interval.
When anything alters red blood cell lifespan: anaemia, haemoglobin variants such as sickle cell trait, recent blood loss or transfusion, pregnancy, and some kidney and liver conditions.
In those cases clinicians may use fructosamine, continuous glucose monitoring or direct glucose testing instead. If your A1C and your readings persistently disagree, mention it.
Problems people actually run into
Treating A1C as the only number that matters
Two people can share an A1C of 7% with very different patterns: one steady near 154 mg/dL, the other swinging between severe lows and highs that average out.
Time in range and glucose variability, which continuous monitoring shows, capture what an average cannot. A1C is one dimension of the picture.
Reading a single result as a diagnosis
Diagnosis normally requires a repeat test or confirmation by a second test type. A single A1C can be affected by illness, recent blood loss or lab variation.
Equally, a result in the prediabetes band is genuinely worth acting on. It is often reversible with sustained changes to diet, weight and activity, and this is the stage where that works best.
Results are estimates for general information only and are not professional financial, medical, or legal advice. Read our full disclaimer.
Sources
- The A1C Test and Diabetes · National Institute of Diabetes and Digestive and Kidney Diseases
Last updated: September 4, 2026