Kilometers (km)
The kilometer is a metric unit of length equal to 1,000 meters. It is used as a standard measure for distances in the SI system, where one meter is defined by the speed of light in vacuum. The kilometer facilitates expressing larger distances conveniently [bipm-si-brochure].
Origin
The kilometer was established in France during the metric system's creation in the late 18th century as 1,000 meters. It was adopted internationally to provide a uniform length measurement for land distances and mapping [bipm-si-brochure].
Worldwide Use
Kilometers are widely used globally for road distances, geography, and transportation metrics. Countries including Canada, Australia, and most of Europe use kilometers for speed limits and distance signs, following SI conventions [nist-si-guide].
Common References
- A marathon race covers 42.195 kilometers
- The average car travels about 15 kilometers per liter of fuel
- Earth's equatorial circumference is approximately 40,075 kilometers
- A typical city block is about 0.1 kilometers long
- Walking speed averages roughly 5 kilometers per hour