The main metric unit of speed is metres per second (m s-1, m·s-1, m/s, mps) however few people will actually use this on a day to day basis, instead they will use kilometres per hour (kph, kmph, km/h, km h-1, km·h-1). One metre per second is 3.6 kilometres per hour.
For some uses in astronomy kilometres per second (kps, kmps, km/s, km s-1, km·s-1) are used, with the speed of light being 299,792.458 km/s or 299,792,458 m/s.
|Unit||Abbreviation||As m/s||Useful Information|
|millimetres per second||mm s-1||0.001||Rarely used|
|centimetres per second||cm s-1||0.01||Rarely used|
|decimetres per second||dm s-1||0.1||Rarely used|
|metres per second||m s-1||1||Used for many scientific velocity calculations|
|decametres per second||dam s-1||10||Rarely used|
|hectometres per second||hm s-1||100||Rarely used|
|kilometres per second||km s-1||1000||Used in astronomical measurements and calculations|
|kilometres per hour||km h-1||0.27778||Commonly used for road speed limits, alternate abbreviations include kmph and kph|
For those countries that use imperial distances the most common unit of speed is miles per hour (mph, miph, m/h, mi/h). Occasionally inches per second (in/s, ips), feet per second (ft/s, fps), yards per second (yd/s, yps) and miles per second (mi/s, m/s, mps) are also seen. It is extremely rare to see the -1 superscript notation used for imperial speed unit abbreviations.
|Unit||Abbreviation||As m s-1||Useful Information|
|inches per second||in/s||0.0254||Rarely used|
|feet per second||ft/s||0.3048||Rarely used|
|yards per second||yd/s||0.9144||Rarely used|
|miles per second||mi/s||1609.344||Rarely used|
|miles per hour||mph||0.44704||Commonly used for road speed limits. Other abbreviations include mi/h, miph, m/h|