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# Convert Kilometer to Millimeter

Please provide values below to convert kilometer [km] to millimeter [mm], or vice versa.

 From: kilometer To: millimeter

### Kilometer

Definition: A kilometer (symbol: km) is a unit of length in the International System of Units (SI). One kilometer is equivalent to 0.6214 miles.

History/origin: The prefix kilo- is a metric prefix indicating one thousand. One kilometer is therefore one thousand meters. The origin of the kilometer is linked to that of the meter, and its current definition as the distance traveled by light in 1/299 792 458 second. This definition is subject to change, but the relationship between the meter and the kilometer will remain constant.

Current use: It is currently the official unit of measurement for expressing distances between geographical places on land in most of the world. However, there still remain a number of countries that primarily use the mile instead of the kilometer including the United States and the United Kingdom (UK). Unlike the United States, the UK has adopted the metric system; while the metric system is widely used in government, commerce, and industry, remnants of the imperial system can still be seen in the UK's use of miles in its road systems.

### Millimeter

Definition: A millimeter (symbol: mm) is a unit of length in the International System of Units (SI). It is defined in terms of the meter, as 1/1000 of a meter, or the distance traveled by light in 1/299 792 458 000 of a second.

History/origin: The milli- prefix is one of many metric prefixes. It indicates one thousandth of the base unit, in this case the meter. The definition of the meter has changed over time, the current definition being based on the distance traveled by the speed of light in a given amount of time. The relationship between the meter and the millimeter is constant however. Prior to this definition, the meter was based on the length of a prototype meter bar. In 2019, the meter has been re-defined based on the changes made to the definition of a second.

### Kilometer to Millimeter Conversion Table

Kilometer [km]Millimeter [mm]
0.01 km10000 mm
0.1 km100000 mm
1 km1000000 mm
2 km2000000 mm
3 km3000000 mm
5 km5000000 mm
10 km10000000 mm
20 km20000000 mm
50 km50000000 mm
100 km100000000 mm
1000 km1000000000 mm

### How to Convert Kilometer to Millimeter

1 km = 1000000 mm
1 mm = 1.0E-6 km

Example: convert 15 km to mm:
15 km = 15 × 1000000 mm = 15000000 mm