Convert from mile/hour to kilometer/hour

Unit Definition (mile/hour)
The mile per hour is a unit of speed, expressing the number of international miles covered per hour. It is currently the unit used for speed limits, and speeds, on roads in the United Kingdom, United States and other nations. It is also used to express the speed of delivery of a ball in various sporting events, such as cricket, tennis, and baseball at the higher levels of competition. A common abbreviation is mph or MPH, although mi/h is sometimes used in technical publications. In the International System of Units (SI), the unit of speed or velocity is m/s. Road traffic speeds, in most countries, are quoted in km/h. Nautical and aeronautical applications, however, favor the knot as a common unit of speed: one knot is one nautical mile per hour.

Unit Definition (kilometer/hour)
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