This page allows you to convert length values **expressed in thou** to **their equivalent in millimeters**.

Enter the value in thou in the top field (the one marked "thou"), then press the "Convert" button or the "Enter" key. The converter also works the other way round: if you enter the value in millimeters in the "mm" field, the equivalent value in thou is calculated and displayed in the top field.

Where L_{thou} is the length in thou and L_{millimeters} is its equivalent in millimeters.

The **thou** is a unit of measure for length equivalent to 1/1000 of an inch, that is 0.001 inches. It is also known as 'mil'. Introduced around 1844, it is still used today in manufacturing specifications of certain products such as printed circuit boards (ex. size of via holes and distance between lines), paper thickness (ex. newspaper paper thickness is around 2 to 4 thou), latex gloves.

One millimeter, in the metric system, is equivalent to 1/1000 (one thousandth) of a meter. **1 mm = 10 ^{-3} m**.

It is used to describe lengths that are relatively small, like the widths of pipes, cables or connectors. The well known terms 8mm, 16mm and 32mm describe common widths of motion picture films.

To understand the approximate size of one millimeter, see this tiny red line: . And this line should be approximately five millimeters long: