Convert a blood glucose reading between mg/dL (used in the US) and mmol/L (used in most other countries). Pick when it was measured to see where the value sits against fasting, after-meal or diabetes target ranges.
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Type the number shown on your meter or lab report
Enter your values to see the result.
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How to use the Blood Sugar Converter
Choose the direction: mg/dL → mmol/L or mmol/L → mg/dL.
Type your reading exactly as your meter or lab report shows it.
Pick when it was measured: fasting, 2 hours after eating, random, or a diabetes before/after-meal target.
Read the converted value and the range it falls in on the color band.
Use the chart below to look up other readings, or copy the result.
Blood sugar conversion formula
mmol/L = mg/dL ÷ 18.016
mg/dL = mmol/L × 18.016
The factor comes from the molar mass of glucose, 180.16 g/mol: one millimole per liter is 180.16 mg per liter, which is 18.016 mg per deciliter (a deciliter is a tenth of a liter). Dividing or multiplying by 18 gives the same answer to one decimal place for almost every reading, which is why many charts simply use 18. US meters show whole numbers in mg/dL; meters set to mmol/L show one decimal.
Blood glucose reference ranges
Values from the American Diabetes Association Standards of Care (2025) for plasma glucose. Individual targets for people with diabetes are set with their care team and may be looser or tighter.
Situation
mg/dL
mmol/L
Meaning
Fasting
70–99
3.9–5.5
Normal
Fasting
100–125
5.6–6.9
Prediabetes (impaired fasting glucose)
Fasting
126 or more
7.0 or more
Diabetes threshold (confirmed by repeat test)
2 h after 75 g glucose (OGTT)
under 140
under 7.8
Normal
2 h after 75 g glucose (OGTT)
140–199
7.8–11.0
Prediabetes (impaired glucose tolerance)
2 h after 75 g glucose (OGTT)
200 or more
11.1 or more
Diabetes threshold
Random, with classic symptoms
200 or more
11.1 or more
Diabetes threshold
Before meals, adults with diabetes
80–130
4.4–7.2
Common target
1–2 h after a meal, adults with diabetes
under 180
under 10.0
Common target
Any time
under 70
under 3.9
Level 1 hypoglycemia
Any time
under 54
under 3.0
Level 2 hypoglycemia
Tips for reading meter results
Check the unit first. A reading of 6 is normal in mmol/L but would be impossible in mg/dL; 108 is normal in mg/dL but impossible in mmol/L. The converter warns you when a number looks like the other unit.
Home meters measure capillary blood but are calibrated to report plasma-equivalent values, so they can be compared with the lab ranges above. Expect meter readings to differ from lab results by up to about 15%.
Continuous glucose monitors (CGMs) read interstitial fluid, which lags blood glucose by roughly 5–15 minutes, so the numbers differ most when glucose is rising or falling fast.
Do not mix up glucose and A1C. A1C is a percentage that reflects the average over about three months; use the A1C calculator to turn it into an estimated average glucose.
Frequently asked questions
How do I convert mg/dL to mmol/L?
Divide by 18 (more exactly 18.016). For example 100 mg/dL ÷ 18.016 = 5.55 mmol/L, which meters show as 5.6. To go from mmol/L to mg/dL, multiply by 18.016: 7.0 mmol/L × 18.016 ≈ 126 mg/dL.
Why is the conversion factor 18?
mmol/L counts glucose molecules, mg/dL counts their weight. One mole of glucose (C6H12O6) weighs 180.16 g, so 1 mmol/L equals 180.16 mg per liter, or 18.016 mg per deciliter. The factor only applies to glucose; cholesterol and other substances use different factors.
What is a normal fasting blood sugar?
According to the American Diabetes Association, a fasting plasma glucose of 70–99 mg/dL (3.9–5.5 mmol/L) is normal, 100–125 mg/dL (5.6–6.9 mmol/L) is the prediabetes range and 126 mg/dL (7.0 mmol/L) or higher on two tests is the diabetes threshold.
What blood sugar is normal 2 hours after eating?
On a standard 2-hour oral glucose tolerance test, under 140 mg/dL (7.8 mmol/L) is normal, 140–199 mg/dL (7.8–11.0 mmol/L) is impaired glucose tolerance and 200 mg/dL (11.1 mmol/L) or more is in the diabetes range. After an everyday meal, people without diabetes usually return below 140 mg/dL within two to three hours.
What counts as low blood sugar?
Below 70 mg/dL (3.9 mmol/L) is level 1 hypoglycemia and below 54 mg/dL (3.0 mmol/L) is level 2, which needs prompt treatment. Level 3 is any low that requires help from another person, regardless of the number.
Which countries use mg/dL and which use mmol/L?
mg/dL is standard in the United States and is also used in some other countries such as Japan, France, India and several in Latin America. The UK, Canada, Australia, China and much of Europe report blood glucose in mmol/L. Many meters can be switched, so check the unit on the display.
Can this converter tell me if I have diabetes?
No. It converts units and shows published reference ranges for information only. Diabetes is diagnosed by a healthcare professional from repeated laboratory tests such as fasting glucose, an oral glucose tolerance test or A1C.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.