How is A1C converted to average blood sugar?

Multiply the A1C by 28.7 and subtract 46.7 to get mg/dL; divide that by 18 for mmol/L. 7% → 28.7 × 7 − 46.7 = 154 mg/dL, or 8.6 mmol/L. The ADA's reference table: 6% = 126, 7% = 154, 8% = 183, 9% = 212, 10% = 240 mg/dL.

What is a normal A1C?

The American Diabetes Association treats below 5.7% as the normal range, 5.7–6.4% as prediabetes and 6.5% or higher, confirmed on repeat testing, as diabetes. In IFCC units those are below 39, 39–47 and 48 mmol/mol and above. Targets for someone already diagnosed are set individually and are often below 7%.

What does an A1C of 6.5 mean in blood sugar?

About 140 mg/dL (7.8 mmol/L) as an average over the previous two to three months. It is also the level at which the ADA's diabetes range begins, though a diagnosis needs the result repeated or confirmed with a glucose test.

How do I convert A1C % to mmol/mol?

IFCC mmol/mol = 10.93 × A1C% − 23.5. So 6.0% = 42, 7.0% = 53, 8.0% = 64 mmol/mol. UK, Australian and many European labs report in mmol/mol; US labs report the percentage. The page shows both for whatever you enter.

Can I work out my A1C from my glucose meter readings?

Only roughly. Average all your readings over two to three months, enter that in 'average glucose → HbA1c', and the page gives the A1C that average would correspond to on the ADAG line. Meter readings cluster around meals and fasting rather than sampling the whole day, so the estimate can be off by half a percentage point or more; a CGM's 90-day average is closer.

A1C to Glucose Calculator (eAG, mmol/L and mmol/mol)

HbA1c to estimated average glucose and back, in mg/dL, mmol/L and IFCC mmol/mol.

Inputs

Convert

HbA1c (%)

320

Average glucose

50500

Glucose unit

Include CalculateEveryday mark

Estimated avg. glucose

140 mg/dL

6.5

Diabetes

NormalPrediabetesDiabetes

Working: 28.7 × 6.5 − 46.7 = 139.8 mg/dL
eAG in mmol/L: 7.8 mmol/L (÷ 18.0182)
HbA1c in IFCC units: 48 mmol/mol
Reference range (ADA): 6.5% or above — diabetes range

ADAG formula: eAG (mg/dL) = 28.7 × A1C − 46.7. Not a diagnosis — confirm with a clinician.

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What each A1C to Glucose input means

Convert: HbA1c → estimated average glucose, or average glucose → estimated HbA1c.
HbA1c (%): An HbA1c result in percent (NGSP units), as most US labs report it.
Average glucose: An average blood glucose, such as a meter's or CGM's 90-day average, in the unit chosen below.
Glucose unit: mg/dL, used in the US, or mmol/L, used in the UK, Canada and Australia. 1 mmol/L is 18 mg/dL.

A1C to Glucose formula

eAG (mg/dL) = 28.7 × A1C − 46.7 · eAG (mmol/L) = eAG (mg/dL) ÷ 18.0182 · reverse: A1C = (eAG + 46.7) ÷ 28.7 · IFCC (mmol/mol) = 10.93 × A1C − 23.50

\text{eAG}_{\text{mg/dL}} = 28.7 \times \text{A1C} - 46.7 \qquad \text{A1C} = \frac{\text{eAG} + 46.7}{28.7}

HbA1c measures the share of haemoglobin that has glucose attached, which reflects average blood glucose over roughly the past two to three months. The ADAG study (Nathan et al., 2008) followed several hundred people with continuous and fingerstick glucose readings and fitted a straight line between their A1C and their measured average glucose; that line, eAG = 28.7 × A1C − 46.7, is what the American Diabetes Association's own converter uses and what this page uses. Dividing mg/dL by 18.0182 gives mmol/L, the unit used in the UK, Canada, Australia and most of Europe. The same A1C is also reported in IFCC units of mmol/mol on many lab reports outside the US; the NGSP master equation converts one to the other. Run backwards, the formula turns a glucose-meter or CGM average into the A1C it would correspond to — an estimate, since the lab measurement is what counts.

A1C to Glucose worked example

An HbA1c of 6.5%: 28.7 × 6.5 = 186.55, minus 46.7 is 139.85, so the estimated average glucose is about 140 mg/dL — 140 ÷ 18.0182 = 7.8 mmol/L. In IFCC units that A1C is 10.93 × 6.5 − 23.5 = 47.5, reported as 48 mmol/mol. 6.5% is the threshold the ADA uses for a diabetes-range result on repeat testing.

Where the A1C to Glucose calculator can give the wrong answer

eAG is an average, not a target. A person whose glucose swings from 70 to 250 and one who sits at 150 all day can share the same A1C and eAG; the number says nothing about the highs and lows.
The ADAG line is a population fit, and the paper publishes a wide 95% range around every value on it. An individual's CGM average can sit well above or below the eAG for the same A1C, so treat the mg/dL figure as the middle of a range, not a point.
Anaemia, iron deficiency, haemoglobin variants (sickle trait, HbC), recent transfusion, pregnancy and kidney disease all change A1C independently of glucose. In those cases the conversion is unreliable and a clinician may use fructosamine or glucose records instead.
The 5.7% and 6.5% cut-offs shown are the American Diabetes Association's. Other bodies use different ones — the WHO uses 6.5% for diabetes but does not define prediabetes by A1C — and a diagnosis needs a lab test repeated or paired with a glucose test, never a calculator.
Reverse mode assumes the glucose you enter is a true average over weeks. A single fasting reading is not an average and will give a misleading A1C.

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A1C to Glucose FAQ

: Multiply the A1C by 28.7 and subtract 46.7 to get mg/dL; divide that by 18 for mmol/L. 7% → 28.7 × 7 − 46.7 = 154 mg/dL, or 8.6 mmol/L. The ADA's reference table: 6% = 126, 7% = 154, 8% = 183, 9% = 212, 10% = 240 mg/dL.
: The American Diabetes Association treats below 5.7% as the normal range, 5.7–6.4% as prediabetes and 6.5% or higher, confirmed on repeat testing, as diabetes. In IFCC units those are below 39, 39–47 and 48 mmol/mol and above. Targets for someone already diagnosed are set individually and are often below 7%.
: About 140 mg/dL (7.8 mmol/L) as an average over the previous two to three months. It is also the level at which the ADA's diabetes range begins, though a diagnosis needs the result repeated or confirmed with a glucose test.
: IFCC mmol/mol = 10.93 × A1C% − 23.5. So 6.0% = 42, 7.0% = 53, 8.0% = 64 mmol/mol. UK, Australian and many European labs report in mmol/mol; US labs report the percentage. The page shows both for whatever you enter.
: Only roughly. Average all your readings over two to three months, enter that in 'average glucose → HbA1c', and the page gives the A1C that average would correspond to on the ADAG line. Meter readings cluster around meals and fasting rather than sampling the whole day, so the estimate can be off by half a percentage point or more; a CGM's 90-day average is closer.