Definition

1 kilometre per hour is the speed you travel at to cover a distance of 1 kilometre in a time of 1 hour.

Click here for our kilometres per hour to miles per hour converter.

Abbreviation

The formal abbreviation for kilometres per hour is km/h.

Other abbreviations in use include kph and kmph, these are often used on car speedometers and probably came about as a metric equivalent of the mph abbreviation for miles per hour.

History

Kilometres per hour came into common usage sometime during the mid 19th century, during the time of the expansion of the railways and have been widely adopted especially in regard to speed for automobiles. The earliest usage we have found so far is in The Practical Mechanic and Engineer's Magazine in 1846, in an article on European railways See Google Books.

With the introduction of SI units in 1960 the standard abbreviations were formalised, though adoption of these is still not 100%.

In 1975 a European Union directive required the use of the km/h abbreviation on all speedometers on cars sold within the EU.

Kilometres per hour is the most commonly seen metric unit of speed, being used for road speed limit signs in most countries in the world. Although technically a derivative unit, its usefulness as a term for the speed of motor vehicles has perpetuated its widespread use.

1 km/h = 3.6 m/s (metres per second the formal SI unit of speed)

The unit is formally abbreviated by km/h, however kph and kmph are in common use in both the UK and US and can often be seen on car dashboards.

Some Speed Records in Kilometres Per Hour

• Land Speed Record - Thrust SSC (UK) - 1227.986 kph
• Electric Powered Land Speed Record - Buckeye Bullet (US) - 517.942 kph
• Motorcycle Land Speed Record - Top Oil Ack Attack (US) - 605.697 kph
• Rail Speed Record - SNCF TGV POS (F) - 574.80 kph
• Maglev Speed Record - JR-Maglev MLX01 (J) - 581.00 kph
• Water Speed Record - Spirit of Australia (AUS) - 511.13 kph

See our miles per hour page for the speed records in mph