What this calculator does
Mg/dL (milligrams per decilitre) and mmol/L (millimoles per litre) are two ways of expressing a concentration, and lab results for things like blood glucose or cholesterol are reported in one or the other depending on the country and the lab. Converting between them needs the molar mass of whatever is being measured, since a millimole of a heavier molecule weighs more than a millimole of a lighter one.
This converter keeps molar mass as a free, editable field rather than hard-coding it to one substance, so it works for glucose, cholesterol or anything else with a known molar mass. For blood glucose specifically, with the correct 18.0182 factor already built in, the dedicated blood glucose unit converter is the simpler option.
The formula
To go from mg/dL to mmol/L, multiply by 10 (to convert decilitres to litres) then divide by the molar mass in grams per mole. To go the other way, multiply mmol/L by the molar mass then divide by 10. The molar mass is what makes this a substance-specific conversion rather than a single universal factor.
| Term | Meaning |
|---|---|
| mg/dL | Milligrams of a substance per decilitre (100 mL) of fluid, a common lab-result unit in some countries. |
| mmol/L | Millimoles of a substance per litre of fluid, the SI unit used for lab results in most other countries. |
| Molar mass | The mass of one mole of a substance, in grams per mole; glucose is about 180.182 g/mol, but other substances differ. |
The inputs explained
| Field | What to enter |
|---|---|
| Value | The value to convert, in whichever unit you are starting from. |
| Convert | Choose the direction of conversion. |
| Molar mass of substance (g/mol) | Molar mass of the specific substance being measured, in grams per mole. Glucose is 180.182 g/mol by default; change it for a different substance. |
When to use it
Reading a lab result reported in an unfamiliar unit
A result from an overseas lab or an older record may use the other unit to the one you are used to seeing; converting it with the right molar mass puts it on familiar ground.
Comparing results from different substances
Because the molar mass is editable, the same tool handles cholesterol, urea or other analytes reported in mg/dL, not only glucose.
Checking a conversion by hand
Useful for verifying a conversion someone else has quoted, by entering the same molar mass and value and comparing the result.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
Mg/dL to mmol/L at 100 mg/dL, for different molar masses
The same 100 mg/dL reading converted using different substance molar masses.
| Molar mass | Result |
|---|---|
| 180.18 g/mol | 5.550 mmol/L |
| 386.65 g/mol | 2.586 mmol/L |
| 60.06 g/mol | 16.650 mmol/L |
| 28.02 g/mol | 35.689 mmol/L |
| 46.07 g/mol | 21.706 mmol/L |
Glucose (180.182 g/mol) mg/dL to mmol/L, across a range of readings
A range of mg/dL readings converted using the glucose molar mass.
| mg/dL | Result |
|---|---|
| 70 mg/dL | 3.885 mmol/L |
| 100 mg/dL | 5.550 mmol/L |
| 126 mg/dL | 6.993 mmol/L |
| 140 mg/dL | 7.770 mmol/L |
| 180 mg/dL | 9.990 mmol/L |
| 250 mg/dL | 13.875 mmol/L |
Questions
How do I convert mg/dL to mmol/L?
Multiply the mg/dL value by 10, then divide by the molar mass of the substance in g/mol. For glucose, that works out to dividing by about 18.0182.
Is the mg/dL to mmol/L factor the same for every substance?
No. It depends on molar mass, so glucose, cholesterol and other analytes each have a different effective conversion factor. That is why molar mass is a free field here rather than a fixed number.
What is the molar mass of glucose?
180.182 g/mol, which gives the commonly quoted 18.0182 conversion factor between mg/dL and mmol/L for glucose specifically.
Should I use this or the dedicated blood glucose converter?
For blood glucose specifically, the blood glucose unit converter already has the correct factor built in and needs no molar mass entry. Use this general converter for other substances, or to double-check a glucose conversion by hand.
For blood glucose specifically, with the conversion factor already set, see the blood glucose unit converter.