Kilometers per hour (km/h) is the most common speed unit outside the United States, displayed on speedometers and road signs across Europe, Asia, and most of the world. Highway speed limits, weather reports for wind speeds, and vehicle performance figures in these regions all use km/h. One kilometer per hour equals approximately 0.2778 meters per second or about 0.6214 miles per hour.

Miles per hour (mph) is the standard speed unit in the United States, United Kingdom, and a few other countries, used for speed limits, vehicle speedometers, and weather forecasts. American road signs exclusively display speed limits in mph, and car enthusiasts commonly reference 0-60 mph times as a performance benchmark. One mile per hour equals exactly 1.60934 kilometers per hour.