Blood Glucose Converter (mg/dL ↔ mmol/L)
Convert blood sugar readings between mg/dL and mmol/L (divide by 18.016), with the fasting and random glucose thresholds for normal, prediabetes and diabetes in both units.
Last updated: October 2026
Converted glucose
5.55 mmol/L
This calculator gives an estimate for general information only. It is not medical advice and does not replace a doctor, pharmacist or other qualified health professional. Always check with them before acting on the result, especially for medication doses, children, pregnancy or a medical condition, and follow the guidelines of your local health authority.
Formula below · 3 sources (medlineplus.gov, niddk.nih.gov, diabetes.org) · Updated Oct 2026
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About this calculator
The US, and most glucose meters sold there, report blood sugar in milligrams per decilitre (mg/dL). The UK, Canada, Australia and most of Europe report millimoles per litre (mmol/L). The two are related by the molar mass of glucose, 180.16 g/mol:
mmol/L = mg/dL ÷ 18.016, and mg/dL = mmol/L × 18.016.
Most references round the factor to 18, which changes a converted value by less than 0.1%: 100 mg/dL is 5.55 mmol/L by the exact factor and 5.56 by 18. The calculator uses 18.016.
Same glucose, different scale. A fasting glucose of 5.6 mmol/L is 100 mg/dL; 7.0 mmol/L is 126 mg/dL; 11.1 mmol/L is 200 mg/dL. These three are the ADA thresholds for the top of normal, diabetes on a fasting test and diabetes on a random test, which is why they appear in both units in the reference table.
The conversion applies to plasma glucose from a laboratory, to meter readings (modern meters are plasma-calibrated) and to CGM values alike. It does not apply to HbA1c, which has its own units (percent and mmol/mol) and its own converter on this site.
The bands describe a fasting reading for information; the diagnosis of diabetes needs repeat testing and a clinician's assessment.
Common blood glucose values in both units
Scroll sideways to see all columns →
| mg/dL | mmol/L | Meaning |
|---|---|---|
| 54 | 3 | Clinically significant hypoglycaemia |
| 70 | 3.9 | Hypoglycaemia alert level |
| 100 | 5.6 | Upper limit of normal fasting glucose |
| 126 | 7 | Fasting diabetes threshold |
| 140 | 7.8 | Upper limit of normal 2 h after glucose load |
| 180 | 10 | Upper limit of the CGM time-in-range target |
| 200 | 11.1 | Random glucose diabetes threshold |
| 250 | 13.9 | Check ketones (type 1 diabetes) |
How to use
Choose the direction and enter the reading from the meter, CGM or lab report. Example (the defaults): 100 mg/dL → mmol/L. 100 ÷ 18.016 = 5.55 mmol/L, the upper limit of normal fasting glucose. Example mmol/L → mg/dL: a UK reading of 7.8 mmol/L. 7.8 × 18.016 = 140.5 mg/dL, the upper limit of a normal reading two hours after a glucose load.
Frequently asked questions
How do I convert mg/dL to mmol/L?
Divide by 18 (exactly 18.016). 90 mg/dL is 5.0 mmol/L; 126 mg/dL is 7.0; 180 mg/dL is 10.0. To go the other way multiply by 18: 6.0 mmol/L is 108 mg/dL.
Why 18?
Glucose has a molar mass of 180.16 g/mol, so 1 mmol is 180.16 mg. One litre is 10 decilitres, so 1 mmol/L is 180.16 ÷ 10 = 18.016 mg/dL.
What is a normal blood sugar in mmol/L?
Fasting, 3.9-5.5 mmol/L (70-99 mg/dL). Two hours after a meal, below 7.8 mmol/L (140 mg/dL). For people with diabetes the ADA suggests 4.4-7.2 mmol/L (80-130 mg/dL) before meals and below 10.0 mmol/L (180 mg/dL) after, individualized by the care team.
What reading means diabetes?
A fasting plasma glucose of 126 mg/dL (7.0 mmol/L) or more, a 2-hour value of 200 mg/dL (11.1 mmol/L) or more in an oral glucose tolerance test, or a random value of 200 or more with symptoms; the ADA requires two abnormal results unless symptoms are clear. An HbA1c of 6.5% (48 mmol/mol) is an alternative criterion.
Does the conversion work for meter readings and CGM values?
Yes. All are plasma-equivalent glucose, so the same factor applies. Older whole-blood meters read about 11% lower than plasma, but meters sold since the mid-2000s are calibrated to plasma values.
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Sources & references
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