KPH to MPH
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The conversion formula for kilometres per hour (kph, kmph, km/h) to miles per hour (mph, miph, mi/h) conversions is as follows:
The conversion formula for miles per hour (mph, miph, mi/h) to kilometres per hour (kph, kmph, km/h) conversions is as follows:
The kilometre per hour is the most commonly used unit of speed being used for speed limits in countries that have adopted the SI metric system.
The kilometre per hour is defined as the speed when travelling the distance of one kilometre in a time of one hour.
metre and second
The SI base unit of distance is the metre and the base unit of time the second. The kilometre per hour is a derived unit based upon these two units.
Formal: km/h, km h-1 and km·h-1
Other abbreviations that are commonly used are kph and kmph. Less common and older abbreviations include k.p.h., km:h, km/hr, km./hr., kms/hr, kms./hr., k.m.p.h., KMph, km ph, K.P.H., KPH, km. hr., km/hour, km.-hr., km. per hour and Kmph. Over time the use of capitals in the abbreviations has been subject to the trends of the day and where the abbreviation is being used.
The kilometre per hour was not the earliest metric unit of speed adopted, that honour goes to the myriametre per hour (1 myriametre = 10,000 metres = 10 kilometres), but became widely used during the expansion of the railways in the mid 19th century.
In 1972 with the full adoption of SI units across the European Union, the EU formally required the use of the SI kilometers per hour abbreviations (km/h, km h-1 and km·h-1) in all official documents and followed that up with the requirement for km/h on speedometers in 1975.
Kilometres per hour are used in the vast majority of countries around the world and are the most common units for speed limits. Notable exceptions to this are the United States of America and the United Kingdom where miles per hour are still used for speed limits. Belize, Liberia and Myanmar have not yet adopted kilometres per hour for speed limits.
Miles per hour are the main unit of speed used in the United States, United Kingdom and other countries that use imperial or US customary measurements for road signs and speedometers.
Imperial & US Customary
The mile per hour is defined as the speed when travelling a distance of one mile in a time of one hour.
yard and second
Miles per hour is a derived unit based upon units of distance (mile) and time (hour). Each of these units is defined in terms of other units, the mile being defined as 1760 yards and the hour being defined as 3,600 seconds.
The most common abbreviation for miles per hour is mph, with other abbreviations including m.p.h., MPH, M.P.H, m/h, m/hr and mi/hr.
Miles per hour came into common useage during the 18th century with the running of regular stage coaches in the United Kingdom (This link shows an 1825 document specifying a speed of 20mph for waggon post). After this the unit became the de facto standard for speed of locomotives on the railways in countries using imperial or US customary units.
Despite the now almost universal adoption of the metric system, a few countries (again those influenced by the UK and the US) still use miles per hour as their standard for road speed limits.
Miles per hour are used in countries that have not yet fully adopted the metric system, including the United States, United Kingdom, Belize, Liberia and Myanmar.