Thousandth of an inch
A thousandth of an inch is a derived unit of length in a system of units using inches. Equal to 1⁄1000 of an inch, a thousandth is commonly called a thou // (used for both singular and plural) or particularly in North America a mil (plural mils).
|Thousandth of an inch|
|Symbol||thou or mil|
|1 thou in ...||... is equal to ...|
|imperial and US customary systems||0.001 in|
|SI units||25.4 μm|
The words are shortened forms of the English and Latin words for "thousand" (mille in Latin). In international engineering contexts, confusion can arise because mil is a formal unit name in North America but mil or mill is also a common colloquial clipped form of millimetre. The units are considerably different: a millimetre is approximately 39 mils.