Speed is the rate at which someone or something moves or operates or is able to move or operate.

Imperial / American measurements

For the imperial system the standard unit of speed is miles per hour(mph).

Metric measurements

For the metric system the standard unit of speed is kilometres per hour(km/h).

Miles per hour (mph)

Miles per hour (abbreviated mph, MPH or mi/h) is an imperial unit of speed expressing the number of miles covered in one hour.

Kilometers per hour (kph)

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