Kilometres per hour

(For the South African airport with IATA code "KMH", see Johan Pienaar Airport.)

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.

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]

1 Conversions 2 See also 3 References 4 External links

• 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)^[2]
• 1 mile per hour = ~1.61 kilometres per hour
• 1 kilometre per hour = ~0.62 miles per hour

• Orders of magnitude (speed)

1. ^ BIPM brochure (SI reference)
2. ^ 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