Blood Sugar Converter
Type mg/dL or mmol/L in either box — the other value and your reference range appear instantly.
Enter a value in either box to convert
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NormalReference ranges (educational)
| Category | Fasting | 2 hours after eating |
|---|---|---|
| Low (hypoglycemia range) | < 70 mg/dL (< 3.9 mmol/L) | < 70 mg/dL (< 3.9 mmol/L) |
| Normal | 70 – 99 mg/dL (3.9 – 5.5 mmol/L) | < 140 mg/dL (< 7.8 mmol/L) |
| Prediabetes range | 100 – 125 mg/dL (5.6 – 6.9 mmol/L) | 140 – 199 mg/dL (7.8 – 11.0 mmol/L) |
| Diabetes range | ≥ 126 mg/dL (≥ 7.0 mmol/L) | ≥ 200 mg/dL (≥ 11.1 mmol/L) |
Common values at a glance
| mg/dL | mmol/L |
|---|
Educational information only — not medical advice or a diagnosis. Always follow guidance from your doctor or care team for managing your blood sugar.
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Why blood sugar has two different units
A single blood glucose reading gets written two completely different ways depending on where you are in the world. The United States, Japan, and a handful of other countries report it as a mass concentration — milligrams of glucose per deciliter of blood, or mg/dL. Most of Europe, Canada, Australia, and much of the rest of the world use a molar concentration — millimoles of glucose per liter of blood, or mmol/L, the SI-standard unit used across most of clinical chemistry. Neither number is more "correct"; they are two ways of describing the same amount of sugar dissolved in the same volume of blood. The friction shows up the moment a glucose meter bought in one country reports in a unit a doctor, family member, or research paper from another country doesn't use — which is exactly what this converter is for.
The conversion formula
mmol/L → mg/dL: multiply by 18.016
18.016 comes from the molar mass of glucose, about 180.16 grams per mole, divided by 10 to reconcile the deciliter and liter volumes and the milli- and unit-level concentrations in the two unit systems. It is a fixed physical constant for glucose specifically — it is not the same conversion factor used for other blood analytes such as cholesterol or creatinine, each of which has its own molar mass.
Worked examples
Reading the reference ranges correctly
Blood sugar guidelines always specify when the sample was taken, because a normal number two hours after a meal is a high number on an empty stomach. This converter asks for that context up front so the category shown actually matches how the value was measured:
| Category | Fasting (8+ hrs) | 2 hours after eating |
|---|---|---|
| Low | Under 70 mg/dL (3.9 mmol/L) — can occur at any time | |
| Normal | 70–99 mg/dL (3.9–5.5 mmol/L) | Under 140 mg/dL (7.8 mmol/L) |
| Prediabetes | 100–125 mg/dL (5.6–6.9 mmol/L) | 140–199 mg/dL (7.8–11.0 mmol/L) |
| Diabetes range | 126+ mg/dL (7.0+ mmol/L) | 200+ mg/dL (11.1+ mmol/L) |
These figures follow the commonly cited American Diabetes Association thresholds and are close to the World Health Organization's criteria as well, though small differences exist between guideline bodies and countries. A single reading in the prediabetes or diabetes range is a prompt to talk to a doctor, not a diagnosis by itself — clinical diagnosis normally involves repeat testing, an HbA1c blood test, or a formal oral glucose tolerance test.
Common mistakes
- Comparing a fasting number to a post-meal threshold, or vice versa. The exact same 130 mg/dL reading is in the diabetes range fasting but perfectly normal two hours after a meal — always match the number to the right column.
- Treating one high reading as a diagnosis. Guidelines require an elevated result confirmed on a separate day, or a supporting HbA1c or oral glucose tolerance test, before diabetes is diagnosed.
- Mixing up the rounding. 5.5 mmol/L and 5.6 mmol/L both trace back to roughly 99–101 mg/dL because of rounding — treat values within a point or two of a threshold as "near the line" rather than a hard pass/fail.
- Ignoring low readings. Blood sugar under 70 mg/dL (3.9 mmol/L) is flagged as low regardless of fasting or post-meal context, since hypoglycemia can occur at any time, especially for people on insulin or other glucose-lowering medication.
What this converter does not do
This tool performs unit arithmetic and shows where a number sits against commonly published reference ranges — nothing more. It cannot measure your blood sugar, does not know your medication, medical history, or how the sample was collected, and it is not a substitute for an actual glucose meter, a lab test, or advice from your doctor or diabetes care team. If you manage a diagnosed condition, always follow the target range and testing schedule your care team has given you rather than the general population figures shown here.
Sources & further reading
- American Diabetes Association — diagnostic thresholds for fasting, post-meal and A1C glucose levels
- CDC Diabetes — reference ranges, prediabetes criteria and testing guidance
- World Health Organization — international diabetes definitions and mmol/L reporting standards
- NIH NIDDK — low blood glucose (hypoglycemia) and blood sugar monitoring basics
Frequently asked questions
What is the formula to convert blood sugar from mg/dL to mmol/L?
Divide the mg/dL reading by 18.016 to get mmol/L, or multiply mmol/L by 18.016 to get mg/dL. The number 18.016 comes from the molar mass of glucose (about 180.16 g/mol) divided by 10, since 1 mmol/L means 1 millimole of glucose per liter of blood. For example, 100 mg/dL ÷ 18.016 ≈ 5.6 mmol/L, and 5.6 mmol/L × 18.016 ≈ 100.9 mg/dL. This converter does that division for you instantly in both directions as you type.
What is a normal fasting blood sugar level?
For most healthy adults with no food for at least 8 hours, a fasting blood sugar under 100 mg/dL (5.6 mmol/L) is generally considered normal. A reading of 100-125 mg/dL (5.6-6.9 mmol/L) falls in the prediabetes range, often called impaired fasting glucose, and 126 mg/dL (7.0 mmol/L) or higher on more than one occasion is in the range associated with diabetes. These figures follow commonly cited American Diabetes Association criteria; your own target range may differ if you have a diagnosed condition, so always follow your care team's guidance.
What counts as a normal blood sugar level 2 hours after eating?
Two hours after starting a meal, or during a 75g oral glucose tolerance test, a reading under 140 mg/dL (7.8 mmol/L) is generally considered normal. 140-199 mg/dL (7.8-11.0 mmol/L) falls in the prediabetes range, often called impaired glucose tolerance, and 200 mg/dL (11.1 mmol/L) or higher is in the range associated with diabetes. Post-meal numbers are naturally higher than fasting numbers, which is why this converter lets you pick the context before checking a reading against the reference table.
Why do some countries use mg/dL and others use mmol/L?
It's mostly historical convention rather than anything about the blood itself. The United States, Japan and a few other countries report glucose as a mass concentration, milligrams of glucose per deciliter of blood (mg/dL). Most of Europe, Canada, Australia and much of the rest of the world report it as a molar concentration, millimoles of glucose per liter of blood (mmol/L), the SI-standard unit. Neither unit is more accurate than the other — they describe the same measurement two different ways, which is exactly what this converter bridges.
Can this blood sugar converter replace a glucose meter or medical advice?
No. This tool only converts and classifies numbers you already have from a glucose meter, lab test or continuous glucose monitor — it cannot measure your blood sugar itself. The reference ranges shown are educational, general-population figures, not a diagnosis, and they don't account for medication, illness, pregnancy or other individual factors. Always rely on an actual meter or lab test for real readings, and talk to your doctor or care team about the target range and next steps that are right for you.