Thousandth of an inch

Thou (short for thousandth of an inch) is a measure of length in the Imperial measurement system and the English name for the American measure of length mil (from Latin millesimus ). 1 Thou is a thousandths of an inch, so it corresponds to 25.4 microns.

The Anglo-American system of measurement has its origins in older English systems, and was before the introduction of the metric system in other Commonwealth countries used ( the imperial system in 1824 ). Today, they are used almost exclusively in the United States ( customary units), while they were officially used in the 20th and much of the 19th century in the United Kingdom and its colonies.

Thou is often used for uniformity measurements, the same significant mil for measurements of electronic components, the design of printed circuit boards and the thickness value of films and coatings. The unit mils is used also in connection with mechanical vibrations.

• Anglo-American unity
• Unit of length
• Abbreviation