A1C & Blood Sugar Converter
Convert an A1C between percent and mmol/mol, turn it into an estimated average glucose, and convert blood sugar between mg/dL and mmol/L. Results are placed against the American Diabetes Association’s 2026 ranges.
How to Use
- Pick what you have: an A1C result, an average glucose (from a meter or CGM report), or a single blood-sugar reading.
- Type the number and choose its unit: A1C in % or mmol/mol, glucose in mg/dL or mmol/L.
- For a single reading, say which test it was (fasting, 2 hours into a glucose tolerance test, random, or other) so the right ADA range is used.
- Read the conversions and where the number sits among the American Diabetes Association 2026 ranges; the scale shows it against the bands.
- Show Work lists every step: the NGSP equation for mmol/mol, the ADAG line for average glucose and the molar mass of glucose for mg/dL ↔ mmol/L.
Worked Example
An A1C of 7%. The ADAG equation gives an estimated average glucose of 28.7 × 7 − 46.7 = 154.2 mg/dL, and dividing by 18.016 turns that into 8.56 mmol/L. In IFCC units the same result is (7 − 2.152) ÷ 0.09148 = 53.0 mmol/mol. It is above the ADA’s 6.5% line, so it sits in the diabetes range; on its own, one result is not a diagnosis.
A fasting reading of 6.1 mmol/L. Multiply by 18.016: 6.1 × 18.016 = 109.9 mg/dL, about 110 mg/dL. For a fasting test the ADA’s prediabetes range is 100–125 mg/dL (5.6–6.9 mmol/L), so this reading falls inside it.
The common mistake: multiplying a percent A1C by 10.93 to get mmol/mol. The two scales do not start at the same zero. 7 × 10.93 gives 76.5 mmol/mol, which is really an A1C of 9.15%. The NGSP equation subtracts 2.152 first: (7 − 2.152) ÷ 0.09148 = 53 mmol/mol.
Show Work
Formulas
Where the Numbers Come From
A1C measures the share of haemoglobin with glucose attached. Red blood cells live about 120 days, so the result is a weighted average of the last few months that leans towards recent weeks. In the United States it is reported in percent, standardised by the National Glycohemoglobin Standardization Program (NGSP) to the assay used in the Diabetes Control and Complications Trial (DCCT); the ADA asks for an NGSP-certified method for diagnosis.
The International Federation of Clinical Chemistry (IFCC) built a reference method that measures glycated haemoglobin directly, with mass spectrometry and capillary electrophoresis, and reports it in mmol per mol of haemoglobin. NGSP and IFCC compared their networks and published a master equation linking the two scales, NGSP = 0.09148 × IFCC + 2.152, which this converter uses.
The A1C-Derived Average Glucose (ADAG) study, led by David Nathan and published in Diabetes Care in 2008, followed 507 people with type 1 diabetes, type 2 diabetes or no diabetes at ten international centres. Each had about 2,700 glucose values over three months from continuous monitoring and fingerstick checks. The straight line A1C to average glucose, 28.7 × A1C − 46.7, fitted with R² = 0.84 and did not differ by age, sex, diabetes type, ethnicity or smoking.
The diagnostic ranges are from section 2 of the American Diabetes Association’s Standards of Care in Diabetes—2026. They apply to people who are not pregnant; pregnancy has its own tests and cut-offs.
About This Tool
This converter works three ways: from an A1C (in % or mmol/mol) to the other unit and an estimated average glucose, from an average glucose back to an estimated A1C, and between mg/dL and mmol/L for a single reading. The glucose factor comes from the molar mass of glucose worked out from the IUPAC atomic weights, not from a rounded 18. Each result is placed against the ADA 2026 ranges for the test you choose, using the ADA’s own figures in the unit you typed, and the scale draws it among the bands.
The ranges describe where a number falls; they do not diagnose diabetes. The ADA asks for two abnormal results (or unmistakable symptoms with a random glucose of 200 mg/dL or more), and A1C can be misleading with anaemia, some haemoglobin variants, dialysis or erythropoietin treatment. For general information only — not medical advice. Talk to a doctor or other qualified professional about your own health.
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Frequently Asked Questions
How do I convert blood sugar from mg/dL to mmol/L?
Divide by 18.016. A millimole of glucose (C₆H₁₂O₆) weighs 180.156 mg, so 1 mmol/L is 180.156 mg in a litre, or 18.016 mg in each of its 10 decilitres. A reading of 110 mg/dL is 6.11 mmol/L, and 7.0 mmol/L is 126 mg/dL.
What average glucose does an A1C correspond to?
The ADAG study (Nathan et al., 2008) found average glucose (mg/dL) = 28.7 × A1C − 46.7. An A1C of 6% matches about 126 mg/dL (6.97 mmol/L), 7% about 154 mg/dL (8.56 mmol/L), 8% about 183 mg/dL and 9% about 212 mg/dL.
How do I change an A1C from percent to mmol/mol?
Use the NGSP master equation, NGSP % = 0.09148 × IFCC + 2.152, rearranged: mmol/mol = (% − 2.152) ÷ 0.09148. So 6.5% is 47.5, which rounds to 48 mmol/mol, and 53 mmol/mol is 7.0%.
What A1C and fasting glucose ranges does the ADA use?
In the ADA Standards of Care 2026 (nonpregnant adults), an A1C of 5.7–6.4% (39–47 mmol/mol) or a fasting glucose of 100–125 mg/dL (5.6–6.9 mmol/L) is the prediabetes range; 6.5% (48 mmol/mol) or more, or a fasting glucose of 126 mg/dL (7.0 mmol/L) or more, is the diabetes range. A diagnosis needs a second abnormal result unless symptoms are unmistakable.
Why doesn’t my meter average match my A1C exactly?
The ADAG line is a best fit across 507 people (R² = 0.84), so individuals sit above or below it. A1C also depends on red blood cells, which live about 120 days; anaemia, some haemoglobin variants and the G6PD variant (in people homozygous for it, A1C reads about 0.7–0.8 points lower) can shift it. A meter average of 154 mg/dL suggests an A1C near 7.0%, but the lab result is the measured value.
How do I use the A1C & Blood Sugar Converter?
Simply type or paste your value and read the result, which refreshes the instant you change something. There is nothing to submit and nothing to wait for.
Is it free? Does it work without internet?
Yes to both. It is free with no sign-up, and once the page has loaded it keeps working even with no internet.
Where does my data go?
Nowhere — every calculation runs on your own device. Nothing you enter is uploaded, logged, or stored.
Common Use Cases
Reading a lab report
A UK or European report gives 53 mmol/mol: that is 7.0% in the US units, with an estimated average glucose of 154 mg/dL (8.56 mmol/L).
Meter readings abroad
A meter set to mmol/L shows 6.1 before breakfast; that is 110 mg/dL, inside the ADA fasting prediabetes range of 100–125 mg/dL.
Making sense of a CGM report
A 14-day average glucose of 154 mg/dL corresponds to an A1C of about 7.0% (53 mmol/mol) by the ADAG equation.
Glucose tolerance test
A 2-hour value of 165 mg/dL (9.16 mmol/L) sits in the ADA 140–199 mg/dL prediabetes range for the 75-g test.
Checking a target
An A1C of 5.4% is 36 mmol/mol, below the 5.7% prediabetes range, with an estimated average glucose of 108 mg/dL (6.01 mmol/L).
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