Convert millimeter to kilometer

Symbol

The millimeter is represented by the symbol "mm." 

Description

Millimeter is an SI (International System of Units) unit of length. It is usually the smallest measure in rulers of the metric system.The word "milli" is derived from the Latin word mille, which means one thousandth. Therefore, a meter is equivalent to a thousand times a millimeter.

The international definition of meter which is the SI base unit of length, is the length of path that light takes in the vacuum over a period of 1/299 792 458 of a second. Thus, 1 millimeter is equivalent to 1/1000 meter. That implies that a millimeter is the distance that light travels in the vacuum in 1/299792458000 seconds.

Following that, there are 10 millimeters in a centimeter and 100 millimeters in a decimeter. In the other direction, a millimeter is equivalent to 1/10 centimeters. A millimeter is also equivalent to 1000 micrometers.

Interestingly the smallest dimension human eyes can detect is about 0.02 to 0.04 mm. This is about the thickness of human hair!

History

The term millimeter was first used in the late 1700s. It was introduced during the development and adoption of the metric system of weights and measures in France in 1795.

The first recorded use of the millimeter was in the Journal of Natural Philosophy in 1797, according to OED (Oxford English Dictionary).

Use

Millimeter is a very small unit of measure. Therefore it is usually used for measuring minute dimensions. 

Symbol

Kilometer is frequently represented by the symbol ‘km’. In the US, UK, and Canadian militaries, the word "klick" is a slang term of the kilometer.

Description

Kilometer is a unit of length in the International System of Units (SI). It is equal to one thousand meters. The kilometer is the preferred measurement unit to express distances between geographical places on land in most of the world. The United States and the United Kingdom are the notable exceptions where the statute mile is used.

A kilometer is equivalent to one thousand meters. So, one kilometer can be written in scientific notations as 1×10^3 m (engineering notation) or 1 E+3 m (exponential notation) — both meaning 10^3 × 1 m.

There are 0.621 statute miles in a kilometer. This means 1 statute mile is equivalent to 1.60934 kilometers. So to convert mile to km, multiply the mile with 0.621.

A kilometer is also equivalent to 3281 feet. In reverse, 1 foot equals 1/3281 kilometers. For calculation of km to yd (kilometer to yards), remember that there are 1094 international yards in a kilometer. If you want to convert nautical miles to km, then multiply kilometer value by 0.540.

History

The term kilometer was first used in the 1800s. It was introduced during the development and adoption of the metric system of weights and measures in France in the late 1700s.

The term "myriamètre"(preferring 10,000 meters) was used several times in 1802. It was used in the text of Develey's book Physique d'Emile: ou, Principes de la science de la nature.

It was first recorded as "kilometer' in 1800-1810. In 1835, French maps were published in which scales are shown in kilometers. The term "kilometer" first became an official unit in 1867  in the Netherlands representing 1000 meters.

Finally, the prefix "myria-" and the associated "myriametre" were officially removed by the International Committee for Weights and Measures (CIPM) in 1935, designating the term "kilometer" as the accepted unit of length for measurements.

Use

This is the go-to unit for expressing land distances, road length etc.