A1C calculator: convert A1C to average glucose

Estimated average glucose at A1C 6%worked example

126 mg/dL

The other glucose unit: 7 mmol/L
A1C in IFCC units: 42 mmol/molUK, AU and much of the EU report this
ADA range: the range the ADA defines as prediabetes

The ADA describes 6% as the range the ADA defines as prediabetes. That is a definition of a numeric range, not a conclusion about you — the ADA asks clinicians to confirm a result with a repeat test and to read it alongside your history and your other results.

Which way are you converting?

Your A1C (%)As printed on your lab report, in NGSP percent.

Glucose unit

Defaulted from your region (United States reports mg/dL).

Previous A1C (optional)To see whether a change is bigger than the assay's own margin.

A1C to estimated average glucose, and the units other countries report
A1C (NGSP %)	eAG (mg/dL)	eAG (mmol/L)	IFCC (mmol/mol)
5.0%	97	5.4	31
5.5%	111	6.2	37
6.0%	126	7	42
6.5%	140	7.8	48
7.0%	154	8.5	53
7.5%	169	9.4	58
8.0%	183	10.2	64
8.5%	197	10.9	69
9.0%	212	11.8	75
9.5%	226	12.5	80
10.0%	240	13.3	86

mg/dL from Nathan 2008; mmol/L converted from that figure using the glucose factor 18.0182; IFCC via the NGSP master equation. The full value-by-value tables are linked below.

Looking for a specific value? Every tenth from 4.5% to 9.0% has its own page — for example A1C 5.7%, 6.0% or 6.5%. There is also the full conversion chart.

An A1C calculator converts a hemoglobin A1C percentage into an estimated average glucose, in both mg/dL and mmol/L, using the ADA equation eAG = 28.7 x A1C - 46.7 published by Nathan in 2008. It converts in either direction, shows IFCC units, and states which range the ADA defines your figure as falling in.

Estimated average glucose (ADAG / Nathan) — eAG (mg/dL) = 28.7 x A1C - 46.7. Verified 2026-07-30 against Nathan et al., Diabetes Care 2008 (ADAG study) (A population regression: in the ADAG study, individuals at the same A1C had meaningfully different mean glucose. The A1C assay itself carries about +/- 0.5 percentage points under NGSP certification.)
NGSP percent to IFCC mmol/mol — IFCC (mmol/mol) = (NGSP % - 2.15) x 10.929. Verified 2026-07-30 against NGSP - IFCC standardisation and the NGSP/IFCC master equation (The master equation is periodically re-derived from network comparison data; treat converted values as approximate.)
A1C assay tolerance (NGSP certification) — certified assays agree with the reference method within about +/- 0.5 percentage points. Verified 2026-07-30 against NGSP - certification criteria for A1C methods (This is the certification limit for the method, not a confidence interval for one person's result.)

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Frequently asked questions

How do you convert A1C to average blood sugar?

Multiply your A1C by 28.7 and subtract 46.7 to get an estimated average glucose in mg/dL. The equation comes from the ADAG study published by Nathan and colleagues in Diabetes Care in 2008. For mmol/L, divide that result by 18.0182.

What is my A1C if my average blood sugar is 140?

Rearranging the same equation, A1C = (140 + 46.7) / 28.7, which is about 6.5%. The ADA uses 6.5% and above as one of its diagnostic criteria for diabetes, normally requiring a confirmatory test, so a figure at that boundary is worth a conversation with your clinician.

How accurate is an estimated average glucose?

The conversion itself is exact arithmetic, but it comes from a population regression: in the ADAG study, people with the same A1C had meaningfully different mean glucose. The A1C assay also carries about half a percentage point of tolerance under NGSP certification.

Why does my lab report show mmol/mol instead of a percentage?

The UK, Australia and much of Europe report A1C in IFCC units (mmol/mol) rather than NGSP percent. The conversion is (NGSP% - 2.15) x 10.929, so 6.5% is about 48 mmol/mol. This calculator shows both.

What period of time does an A1C reflect?

Roughly the previous two to three months of glucose exposure, weighted towards the most recent weeks. That weighting is why an A1C can move before a full 90 days have passed, and why one value cannot show you a trend.

Is a change between two A1C results meaningful?

Not necessarily. NGSP certification allows a certified assay to differ from the reference method by about 0.5 percentage points, so a change smaller than that may be the test rather than anything that changed in you. Enter a previous value above and the tool will tell you which side of that line you are on.

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The next number

No body metric means much on its own. Here is what this one feeds into.

Glucose to A1C calculatorHolding a meter average rather than a lab report? Convert the other direction.GMI calculatorIf your average came from a CGM, GMI is the equation designed for that data — and the gap against your lab A1C is worth seeing.

Related calculators

Glucose to A1C calculatorGlycemic markers GMI calculatorGlycemic markers

Every formula on this page is listed with its source on the methodology page, and changes to any reference value are logged in the data changelog. Canonical URL: https://myhealthmywellness.com/a1c-calculator