Explaining the Kilometer (km) and Converting to Miles

By: Mitch Ryan  | 
Depending on where in the world you're driving, you might see the speed limit posted in kilometers per hour instead of miles per hour. The conversion make a big difference. mikroman6 / Getty Images

The kilometer (km) is a standard unit of measurement used in the metric system. Derived from the French "kilomètre," the unit is used to measure length and distance along a straight path.

You would likely choose kilometers over meters or millimeters to measure roads and other great distances since a broader unit range is needed. Read on to learn more about the metric system and when to use kilometers instead of smaller units of measurement.


How Does the Metric System Work?

The metric system is simple to learn because you can measure distances or volume in multiples of 10. Meters are the standard on which all the other measurement units are based. For example, a centimeter is equal to 1/100th of a meter, and a millimeter is equal to 1/100th of that unit measurement.

That smaller unit range is adequate for calculating the area of a room, but when traveling north on a highway, it would be frustrating trying to estimate such a large measurement of speed or distance with minuscule measurements.


Converting From Imperial to Metric

The imperial system works the same way, except it uses miles, feet and inches in place of kilometers, meters and centimeters.

One mile is equal to 1.609 km, 1 foot equals roughly a third of a meter, and 1 inch is about 2.5 centimeters. Note that, in this conversion, we're referring specifically to a mile on land — not a nautical mile, which is slightly longer (about 1.8 km).


Runners are one of the few groups of people who remember these conversions since races are generally measured in kilometers. But for everyone else, there are several apps and conversion calculators available if you ever need to make a quick distance calculation.

Why Does the American Pronunciation of Kilometer Place Primary Stress on the Second Syllable?

For any country that uses the metric system, the word "kilometer" is generally pronounced with the stress on the first syllable (KI-lo-meter). In contrast, a country like the United States that uses the imperial mile to measure distance may use a pronunciation with stress on the second syllable.

This second pronunciation pattern is also found in examples like speedometer, but the former pronunciation is more accurate, according to the Merriam-Webster dictionary.