To convert kilometers to miles (km to mi), multiply by 0.62137. 1 kilometer equals 0.62137 mi, about 3 times as much as the height of the Eiffel Tower, in Paris.
| kilometers | miles |
|---|---|
| 1 kilometer | 0.62137 mi |
| 2 kilometers | 1.2427424 mi |
| 5 kilometers | 3.106856 mi |
| 10 kilometers | 6.2137119 mi |
| 25 kilometers | 15.53428 mi |
| 50 kilometers | 31.06856 mi |
| 100 kilometers | 62.137119 mi |
| 250 kilometers | 155.3428 mi |
| 500 kilometers | 310.6856 mi |
| 1000 kilometers | 621.37119 mi |
Definition: A kilometer is 1,000 meters - the "kilo" doing the same job it does in kilogram or kilobyte.
History: The meter itself was originally defined, back in 1793 during the French Revolution, as one ten-millionth of the distance from the North Pole to the equator. Today it's defined by how far light travels in a tiny fraction of a second instead - a far more precise anchor - but either way, a kilometer has always just meant a thousand of whatever "one meter" happens to be.
Current use: Nearly everywhere on Earth measures road distances, race lengths, and everyday travel in kilometers. The US remains one of the few holdouts still measuring road trips in miles.
Definition: A mile is 5,280 feet, or exactly 1,609.344 meters.
History: It started as the Roman "mille passus" - literally a thousand paces, where a pace was a Roman soldier's double-step, about 5 Roman feet. That put the original Roman mile at 5,000 feet. Centuries later, English farmers were measuring land in furlongs (660 feet, the length of a furrow before an ox needed a rest), and in 1593 Queen Elizabeth I's Parliament decided a mile should equal exactly 8 furlongs - bumping the mile from 5,000 feet to 5,280, the number that's stuck ever since.
Current use: The US, UK, and a handful of other countries still measure road distances in miles. Aviation and shipping use a different mile entirely - the nautical mile, based on the Earth's circumference, not Roman soldiers' footsteps.
Since a mile is defined as exactly 1,609.344 metres, this factor is exact and the decimal simply never terminates.
For a quick estimate, multiply by 0.6. That is off by about 3.4%, which is fine for a rough figure and not fine for anything you are paying for or building to. Use the exact factor of 0.621371 when it matters.
Going the other way, one mile is 1.609 km, which is usually the easier direction to work in. Because the forward factor is small, watch the decimal place rather than the digits: a factor-of-ten slip is the common error, not a rounding one.
To anchor the scale: 2 kilometers is about 1.24 mi.