In America, the primary system used for measuring distance is the United States customary units of measurement. The main unit to measure distance is the mile. When measuring the rate at which a vehicle travels, miles per hour are used. Outside of the United States, the main system of measurement is the metric system. This system uses kilometres to measure distance and kilometres per hour to measure rate.

### Miles Per Hour

To measure how fast a vehicle is travelling, Americans use miles per hour. Cars, trains and planes are all clocked using this unit of measurement. Even the speed at which animals run is measured in miles per hour. Miles per hour is commonly referred to as "MPH" The speedometers on cars sold in the United States primarily display the car's current speed in MPH. Local speed limits also are posted in miles per hour.

### Kilometres Per Hour

Those who use the metric system use kilometres per hour, or "KPH," in the same way that those in America use miles per hour. Most parts of the world outside the United States use KPH. Speedometers on automobiles sold abroad have kilometres per hour as their primary designation instead of the regionally irrelevant MPH. Kilometers per hour, or KPH, is also shown on American speedometers, but it usually is written in smaller numbers underneath the meter's MPH readings.

### Reading Miles or Kilometers Per Hour

When reading the speed of a vehicle or another object in either miles per hour or kilometres per hour, the number given is the amount of miles that will be travelled after one hour as long as the speed does not waver. A car travelling 60 miles per hour will have travelled 60 miles after one hour if the car's speed remains constant. A car travelling 60 kilometres per hour will have travelled 60 kilometres after one hour.

### Converting MPH to KPH

One mile is roughly equivalent to 1.609344 kilometres, so to convert miles into kilometres, you must multiply the amount of miles by 1.609344. Using this formula, sixty miles is equivalent to approximately 96.56 kilometres. To convert kilometres into miles, divide the amount of kilometres by 1.609344. A 55 MPH speed limit in America translates to approximately 88.5 KPH. A speed limit of 65 MPH is approximately 104.6 when converted into kilometres per hour.