A meter is the SI unit of distance. The meter is defined as the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 of a second.[1] The meter is defined as a measure of time because time can be measured far more accurately than length (at the time of the definition, time could be measured to 1 part in 1013 whereas length could only be measured to 4 parts in 109).[2]

Metric prefixes make longer units like kilometer, km (1000 m) and megameter, Mm (106 m) and smaller units as well like millimeter, mm (0.001 m) and the μm (10-6 m). The μm is called both the micrometer and the micron. The word micrometer is ambiguous since it's also a device that measures very precise lengths, hence the two terms.

Meter Unit Conversion

Read more about meters Dr. Rowlett's unit dictionary.


  1. NIST. Historical context of the SI [Online]. Available:
  2. New Scientist. (1963). Time to remeasure the metre [Online]. Available:

Authors and Editors

Jordan Hanania, Isaac, James Jenden, Kailyn Stenhouse, Jason Donev