What this glucose converter does
Blood sugar is reported in two different units depending on where you are. The United States and much of Latin America use milligrams per deciliter (mg/dL), while the UK, Canada, most of Europe and much of the rest of the world use millimoles per liter (mmol/L). The same reading — from your glucose meter or a lab panel — can show up as 100 mg/dL or as 5.55 mmol/L. This tool converts any value from one unit to the other in both directions, so a foreign lab report, a research paper or a meter bought abroad never leaves you guessing.
How to use it
- Type the glucose value you have.
- Choose the unit you entered it in: mg/dL or mmol/L.
- The equivalent in the other unit appears instantly.
- Picked the wrong unit? Hit Swap units to flip the direction of the conversion.
When the value is a fasting measurement, the table highlights the guideline category it falls into — normal, prediabetes or diabetes. Everything runs in your browser; no value is ever sent or stored.
The conversion formula
Glucose has a known molecular weight, which gives a fixed conversion factor of 18.0182:
- mg/dL to mmol/L:
mmol/L = mg/dL ÷ 18.0182 - mmol/L to mg/dL:
mg/dL = mmol/L × 18.0182
Plenty of sources round the factor to 18, but 18.0182 is more accurate. Here are common values already converted:
| mg/dL | mmol/L | Fasting reference |
|---|---|---|
| 70 | 3.88 | Low end of normal |
| 90 | 4.99 | Normal |
| 100 | 5.55 | Prediabetes begins |
| 126 | 6.99 | Diabetes threshold |
| 140 | 7.77 | Elevated |
| 200 | 11.10 | Very high |
Worked example
Your meter reads 100 mg/dL and you want it in mmol/L. Divide: 100 ÷ 18.0182 = 5.55 mmol/L. Going the other way, a European lab reports a fasting result of 7 mmol/L and you want mg/dL: multiply 7 × 18.0182 = 126.13 mg/dL — right at the 126 mg/dL line that defines diabetes on a fasting test. That is exactly why 7.0 mmol/L and 126 mg/dL are quoted as the same cut-off.
Fasting reference ranges
The American Diabetes Association (ADA) and WHO criteria for fasting glucose in adults are:
| Category | mg/dL | mmol/L |
|---|---|---|
| Normal | 70 – 99 | 3.9 – 5.5 |
| Prediabetes | 100 – 125 | 5.6 – 6.9 |
| Diabetes | 126 or more | 7.0 or more |
These ranges apply to fasting glucose (no food for at least 8 hours). After a meal, after a tolerance test, or when using HbA1c, the thresholds are different — don’t mix contexts.
Frequently asked questions
Why are there two units for blood glucose?
It is historical and regional. mg/dL states a mass (milligrams) in a volume (deciliter); mmol/L states a number of molecules (millimoles) per liter, the form preferred by the International System of Units. Both measure the same thing on different scales, which is why the fixed factor 18.0182 always converts cleanly between them.
Should I divide by 18 or 18.0182?
Both are in use. 18 is a handy shortcut for mental math; 18.0182 comes from the molecular weight of glucose and is more precise. For 100 mg/dL you get 5.56 with 18 and 5.55 with 18.0182 — a tiny difference, but this converter uses the more exact value.
Does it work for HbA1c?
No. HbA1c is reported as a percentage (%) or in mmol/mol and reflects your average glucose over the past 2 to 3 months, not a single reading. Turning HbA1c into estimated average glucose needs a separate formula, so this tool only handles a point-in-time blood glucose measurement.
Can I diagnose diabetes with this?
No. Converting units and seeing a guideline range is not a diagnosis. Diabetes is confirmed through repeat testing and the judgment of a healthcare professional who weighs your symptoms, history and other results. Treat this as an informational aid and always talk to your doctor.