The kilometre per hour (American English: kilometer per hour) is a unit of speed or velocity, expressing the number of kilometers traveled in one hour. The unit symbol is km/h or km·h⁻¹; however, the colloquial abbreviations "kph" and "kmph" are sometimes also used in English-speaking countries, in analogy to mph, although these are not in accordance with international scientific standards. In North American slang and military usage, km/h (as well as km) is commonly pronounced, and sometimes even written, as klicks or kays (K's), although these may also be used to refer to kilometres.

Worldwide, the km/h is the most commonly used speed unit on road signs and car speedometers. Therefore, it is far more common in everyday usage than the proper SI unit of speed, m/s. Along with the kW·h, km/h is the most commonly used metric unit based on the hour, which is only a "non-SI unit accepted for use with the International System of Units" by the BIPM.^[1]

[edit] Conversions

• 3.6 km/h ≡ 1 m/s, the SI unit of speed, metre per second
• 1 km/h ≈ 0.277 78 m/s
• 1 km/h ≈ 0.621 37 mph ≈ 0.911 34 feet per second
• 1 knot ≡ 1.852 km/h (exactly)
• 1 mile per hour ≡ 1.609344 km/h (~1.61 km/h)^[2]

[edit] See also

• Orders of magnitude (speed)
• Miles per hour

[edit] References

1. ^ BIPM brochure (SI reference)
2. ^ 1 yard ≡ 0.9144 m and
   1 mile = 1760 yards thus
   1 mile = 1760 × 0.9144 ÷ 1000 km

[edit] External links

• kph to mph converter Online conversions for speed units: km/h and mph

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