A kilometer is a unit of distance equal to 1,000 meters, or about 0.62 miles. Most countries around the world use kilometers to measure distances on road signs, maps, and speedometers. If you're driving through Canada, Europe, or Japan, the speed limit signs show kilometers per hour rather than miles per hour.

To picture a kilometer, imagine walking at a normal pace for about 10 to 12 minutes. That's roughly how long it takes most people to cover a kilometer on foot. A marathon race is about 42 kilometers long. Mount Everest, the world's tallest mountain, reaches about 8.8 kilometers above sea level.

Scientists, engineers, and mathematicians prefer the metric system because it's based on units of ten, making calculations simpler. The United States is one of the few countries that still primarily uses miles instead of kilometers, though American scientists use the metric system in their work.

When you see “km” as an abbreviation, that stands for kilometer. A car's odometer in most countries tracks how many kilometers the vehicle has traveled over its lifetime.