What is a Kilometer?

The kilometer equals exactly 1,000 meters and is the international standard unit for road distances, geography, and travel. Adopted as part of the metric system in the 1790s, it became the dominant road-distance unit worldwide except in the United States, the United Kingdom (which uses miles for road signs), and Myanmar. Speed limits across Europe, Asia, Australia, Africa, and Latin America are expressed in km/h. The kilometer's relationship to the meter is decimal and exact, making it ideal for scientific work. A kilometer takes a healthy adult about 12 minutes to walk and roughly 1,250 average steps. Geographic distances — from city blocks to airline routes — are typically given in kilometers, with the Earth's equatorial circumference measuring approximately 40,075 km.

Visual reference for how the kilometer relates to other length units. Each row links to the full converter for that pair.

See all 15 length units in matrix view →

• Motorway distances on road signs across Europe
• Marathon and long-distance running (marathon = 42.195 km)
• GPS navigation and driving directions globally

• ✓1 km ≈ 0.621 miles — a quick mental shortcut is to multiply km by 0.6 (or 5/8).
• ✓To convert km/h to m/s divide by 3.6. Useful in physics problems.
• ✓A kilometer takes a healthy adult about 10–12 minutes on foot or 3 minutes on a bicycle.

• ✗Reading a US speed-limit sign as km/h when it is actually mph — 70 mph is 112 km/h, not 70.
• ✗Using 1.5 instead of 1.609 when converting miles to km on long trips — the error compounds.
• ✗Confusing kilometer (distance) with kilogram (mass). Both abbreviated with "k" prefix but measure different things.