# Metre per second

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Metre per second (U.S. spelling: meter per second) is an SI derived unit of both speed (scalar) and velocity (vector quantity which specifies both magnitude and a specific direction), defined by distance in metres divided by time in seconds.

This is the main unit of speed.

The official SI symbolic abbreviation is m·s−1, or equivalently either m/s or $\tfrac{\mbox{m}}{\mbox{s}}$;[1] although the abbreviation mps is sometimes used colloquially, but is incorrect according to the BIPM. Where metres per second are several orders of magnitude too slow to be convenient, such as in astronomical measurements, velocities may be given in kilometres per second, where 1 km/s is equivalent to 103 metres per second.

## Contents

### Conversions

1 m/s is equivalent to:

foot per second = 0.3048 m·s−1 (exactly)

mile per hour ≈ 0.44704 m·s−1 (exactly)

km·h-1 ≈ 0.2778 m·s−1 (approximately)

1 kilometre per second is equivalent to:

### Relation to other measures

Although m·s−1 is an SI derived unit, it could be viewed as more fundamental than the metre, since the latter is derived from the speed of light in a vacuum, which is defined as exactly 299 792 458 m·s−1 by the BIPM[2]. It follows that one metre is the length of the path travelled by light in a vacuum during a time interval of 1/299 792 458 of one second.