About the Blood Sugar Converter
Blood glucose is measured in two different units depending on where you live: milligrams per decilitre (mg/dL) in the United States and some other countries, and millimoles per litre (mmol/L) in the UK, Canada, Australia and most of Europe. A reading of 100 mg/dL is about 5.55 mmol/L, which can be confusing when you read advice or use a meter from another country. This converter changes one into the other using the factor 18.02 and also shows a simple range check for adults, depending on whether the reading was taken fasting or two hours after a meal. It is for understanding units, not for diagnosis or treatment.
Updated October 2026
How to use the Blood Sugar Converter
- 1Choose the unit you are converting from.
- 2Type the blood glucose value.
- 3Tell the tool whether the reading was fasting or after eating.
- 4Read the converted value and the range comment.
- 5Always follow the targets your healthcare team gave you.
Quick reference
- 54 mg/dL = 3.0 mmol/L.
- 70 mg/dL = 3.9 mmol/L.
- 100 mg/dL = 5.55 mmol/L.
- 126 mg/dL = 7.0 mmol/L.
- 140 mg/dL = 7.8 mmol/L.
- 180 mg/dL = 10.0 mmol/L.
Why the units differ
The US uses mass per volume, while most of the world switched to the SI unit of moles per litre for lab results. Glucose has a molar mass of about 180 grams per mole, which gives the conversion factor. When reading research or advice from abroad, check the unit before you compare it with your own numbers, because a reading of 7 looks safe in mg/dL but is quite high in mmol/L.
Fasting and after-meal readings answer different questions. A fasting reading shows how well your body manages sugar when it has not just eaten, while an after-meal reading shows how it copes with a load. Take readings under the same conditions each time, wash and dry your hands first to avoid false highs from food on the skin, and write them down with the time and what you ate so that your care team can spot patterns.
When to seek help
Contact a doctor if you have repeated high readings, symptoms such as extreme thirst, frequent urination or unexplained weight loss, or low readings that you can't explain. For a reading that is very high or very low with symptoms such as confusion, vomiting or fast breathing, seek emergency care at once.
Related tools
The A1C Calculator relates average glucose to long-term control, the Cholesterol Ratio Calculator and GFR Calculator cover other markers, and the Calorie Calculator and Carbohydrate Calculator help you plan meals.
Features
- mg/dL and mmol/L both ways
- Fasting and after-meal ranges
- Warnings for very low readings
- Checks for impossible values
- No data stored
- Free and instant
Frequently asked questions
How do I convert mg/dL to mmol/L?
Divide by 18.02. A reading of 126 mg/dL is 7.0 mmol/L. To go the other way, multiply mmol/L by 18.02, so 5.5 mmol/L is about 99 mg/dL.
What is a normal fasting blood sugar?
For most adults, 70 to 99 mg/dL (3.9 to 5.5 mmol/L). A fasting level of 100 to 125 mg/dL (5.6 to 6.9 mmol/L) is raised, and 126 mg/dL (7.0 mmol/L) or more on repeat tests is in the diabetes range.
What should blood sugar be after eating?
Under 140 mg/dL (7.8 mmol/L) two hours after a meal for people without diabetes. Many people with diabetes aim for under 180 mg/dL (10 mmol/L), but your own target may differ.
What counts as low blood sugar?
Below 70 mg/dL (3.9 mmol/L) is low, and below 54 mg/dL (3.0 mmol/L) is very low and needs prompt treatment. Follow your care team's plan, and seek urgent help for severe symptoms such as confusion or loss of consciousness.
Why do different meters show different numbers?
Meters have an allowed error, often up to 15 percent, and give different results from lab tests. Readings from fingers, arms and continuous monitors can also differ. Use the same meter for trends.
Can I use this for my pet's or child's readings?
The conversion is the same, but target ranges differ for children and animals. Ask the vet or clinician for the right range.