Mils to MM Converter
Convert mils (thou) (mil) to millimeters (mm) instantly. Type a value — the result updates as you type, and the swap button converts the other way.
Mils to mm formula
mm = mil × 0.0254
1 mil (thou) = 0.0254 millimeters · 1 millimeter = 39.37 mils (thou)
To convert mils (thou) to millimeters, multiply the value by 0.0254. For example, 4 mil:
mm = 4 × 0.0254mm = 0.1016
So 4 mil = 0.1016 mm.
Mental math shortcut
This conversion is exact, so there is no need to estimate: just multiply by 0.0254.
Mils to mm conversion table
mm back to Mils
The same values converted the other way, rounded for everyday use:
| Millimeters | Mils (thou) |
|---|---|
| 0.0254 mm | 1 mil |
| 0.0508 mm | 2 mil |
| 0.0762 mm | 3 mil |
| 0.1016 mm | 4 mil |
| 0.1524 mm | 6 mil |
| 0.254 mm | 10 mil |
| 0.508 mm | 20 mil |
| 1.02 mm | 40.16 mil |
About the units
Mils (thou) (mil)
A mil (or thou) is one thousandth of an inch (0.0254 mm). It is used for plastic sheeting, coatings and wire insulation thickness.
Millimeters (mm)
A millimeter is one thousandth of a meter (0.1 cm). It is used for small, precise measurements like rainfall, screws and paper thickness.
Frequently asked questions
How many millimeters are in a mil (thou)?
One mil (thou) equals 0.0254 millimeters.
What is 4 Mils in mm?
4 mil = 0.1016 mm.
How do I convert mm back to Mils?
Divide the millimeters by 0.0254.