The kilometre per hour (American English: kilometer per hour) is a unit of both speed (scalar) and velocity (vector). 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.
The km/h is the worldwide 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.
- 3.6 km/h ≡ 1 m/s, the SI derived 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 = 1.609344 km (~1.61 km)
- 1 mile per hour = ~1.61 kilometres per hour
- 1 kilometre per hour = ~0.62 miles per hour
- ↑ BIPM brochure (SI reference)
- ↑ 1 yard ≡ 0.9144 m and
1 mile = 1760 yards thus
1 mile = 1760 × 0.9144 ÷ 1000 km
- The converter Online conversions for speed units: km/h, mph, knots, etc.
- Online Conversions of Metric and Imperial Units
- Conversion Calculator for Units of Speed
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