The kilometer is an international unit of length for measuring large distances. It equals exactly 1,000 meters.
With the notable exception of the United States and the United Kingdom, the kilometer has become the worldwide standard unit for expressing geographical distances. As a unit of length in the International System of Units (SI), the kilometer measures - as the prefix “kilo” suggests - a thousand times the length of a meter. The Great Wall of China, the longest monument on earth, has a total length of 21,196.18 kilometers.
After the definition of the meter in 1793 in France, the kilometer was initally called “Millaire”. Also, the unit “Myriameter”, which equaled 10,000 meters, was preferred over the meter for several decades.
| Kilometers | |
|---|---|
| Marathon | 42.2 |
| Race track "Mille Miglia" | 1,609.3 |
| Earth radius | 6,378.2 |
| Earth circumference | 40,075.2 |
| Distance earth ↔ moon | 384,400.0 |
| Distance earth ↔ sun | 149,593,780.0 |