# Convert Speed

Speed | |
---|---|

Dimension | LT^{-1} |

Common Symbol(s) | V |

SI Unit(s) | m·s^{-1} |

Imperial/US Unit(s) | mph |

Other Unit(s) | knot |

Unit conversions | |

1 m·s^{-1} in ... |
... is equal to ... |

Metric unit(s) | 3.6 km·h^{-1} |

Imperial/US unit(s) | 2.237 mph |

Nautical unit(s) | 1.944 knot |

**I want to convert:**
**using**

Metric | Conversion |
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Kilometre per second [km/s] | |

Metre per second [m/s] | |

Kilometre per hour [km/h] | |

Millimetre per second [mm/s] | |

Micrometre per second [µm/s] |

Imperial/US | Conversion |
---|---|

Mile per second | |

Mile per hour [mph] | |

Foot per second [ft/s] |

Nautical | Conversion |
---|---|

Knot |

Other | Conversion |
---|---|

Speed of light [c] | |

Speed of sound | |

Human walk | |

Common snail |

In everyday use and in kinematics, the **speed** of an object is the magnitude of its velocity (the rate of change of its position); it is thus a scalar quantity. The average speed of an object in an interval of time is the distance travelled by the object divided by the duration of the interval; the instantaneous speed is the limit of the average speed as the duration of the time interval approaches zero.

**Speed** has the dimensions of distance divided by time. The SI unit of speed is the metre per second, but the most common unit of speed in everyday usage is the kilometre per hour or, in the US and the UK, miles per hour. For air and marine travel the knot is commonly used.

The fastest possible **speed** at which energy or information can travel, according to special relativity, is the speed of light in a vacuum c = 299792458 metres per second (approximately 1079000000 km/h or 671000000 mph). Matter cannot quite reach the speed of light, as this would require an infinite amount of energy. In relativity physics, the concept of rapidity replaces the classical idea of speed.

This article uses material from the Wikipedia article "Speed", which is released under the Creative Commons Attribution-Share-Alike License 3.0.