Speed is the rate at which someone or something moves or operates or is able to move or operate.
For the imperial system the standard unit of speed is miles per hour(mph).
For the metric system the standard unit of speed is kilometres per hour(km/h).
Miles per hour (abbreviated mph, MPH or mi/h) is an imperial unit of speed expressing the number of miles covered in one hour.
Kilometre per hour (American English: kilometer per hour) is a unit of speed, expressing the number of kilometres travelled in one hour. It is also commonly referred to as kph in English-speaking countries. Worldwide, it is the most commonly used unit of speed on road signs and car speedometers.
1 mph = 1.61 kph