Convert mm to inches

Millimeter

Definition: A millimeter (symbol: mm) is a unit of length in the International System of Units (SI). It is defined as 1/1000 meters, making it one tenth of a centimeter.

History/origin: A millimeter is based on the SI unit meter, and as the prefix "milli" indicates, is equal to one thousandth of a meter. The metric system, which includes the millimeter, was first adopted in France in 1795 during the French Revolution. The "milli" prefix comes from the Latin word "mille" meaning thousand. The millimeter is part of the decimal-based metric system where each unit is a power of ten greater or smaller than other related units.

Current use: The millimeter is commonly used worldwide for measuring small distances and lengths. It's frequently used in engineering, manufacturing, and scientific applications where precision is required. Millimeters are used to measure rainfall, the size of small electronic components, thickness of materials, and in medical contexts for precise measurements.

Inch

Definition: An inch (symbol: in) is a unit of length in the imperial and US customary systems of measurement. An inch was defined to be equivalent to exactly 25.4 millimeters in 1959. There are 12 inches in a foot and 36 inches in a yard.

History/origin: The term "inch" was derived from the Latin unit "uncia" which equated to "one-twelfth" of a Roman foot.

There have been a number of different standards for the inch in the past, with the current definition being based on the international yard. One of the earlier definitions of the inch was based on barleycorns, where an inch was equal to the length of three grains of dry, round barley placed end-to-end. Another version of the inch is also believed to have been derived from the width of a human thumb, where the length was obtained from averaging the width of three thumbs: a small, a medium, and a large one.

Current use: The inch is mostly used in the United States, Canada, and the United Kingdom. It is also sometimes used in Japan (as well as other countries) in relation to electronic parts, like the size of display screens.