📏 Miles to Km Converter
Convert miles to kilometres and back. The exact factor, a table of the values people look up most, and what each unit is actually used for.
Converting miles to kilometres
One mile is 1.609344 kilometres, and one kilometre is 0.6213711922 miles.
kilometres = miles × 1.609344
Getting the precision right
One mile is exactly 1.609344 km. The rough conversion of 1.6 is 0.6% low, which on a 100-mile journey is about a kilometre. A neater trick uses the Fibonacci sequence: consecutive terms approximate the ratio, so 5 miles is about 8 km and 8 miles is about 13 km, both accurate to under 0.5%.
Where each unit is used
Miles are used for road distance and speed in the United States and the United Kingdom, and almost nowhere else. The UK is the unusual case: it sells petrol in litres but measures the journey in miles, so fuel economy there is quoted in miles per gallon using a gallon nobody buys.
Values worth knowing
| mi | km |
|---|---|
| 1 | 1.60934 |
| 2 | 3.21869 |
| 5 | 8.04672 |
| 10 | 16.0934 |
| 13.1 | 21.0824 |
| 26.2 | 42.1648 |
| 50 | 80.4672 |
| 60 | 96.5606 |
| 70 | 112.654 |
| 100 | 160.934 |
A half marathon at 13.1 miles is 21.1 km; a marathon at 26.2 miles is 42.2 km. A 70 mph motorway limit is 113 km/h. The 60 mph limit on UK single carriageways is 97 km/h.
Where the two units came from
The mile is Roman: mille passus, a thousand paces, where a pace was two steps. That gave about 1,480 metres. England later redefined it in 1593 as eight furlongs, making it 1,609.344 metres, because the furlong was tied to agricultural land division and could not be adjusted without redrawing field boundaries. The kilometre arrived with the metric system in the 1790s, defined from the metre, which was itself meant to be one ten-millionth of the distance from the equator to the North Pole.
Round the result to the precision your own work needs. These converters carry the full factor, which is useful for checking but rarely what you want to write down.
The natural follow-ups are the cm to inches, for what this figure feeds into, and the feet to cm, for the closely related case.
Frequently Asked Questions (FAQs)
How many kilometres are in a mile?
Exactly 1.609344. The quick version, multiplying by 1.6, is about 0.6% low, which only matters over long distances.
Is there a trick for converting in your head?
Consecutive Fibonacci numbers approximate the ratio well: 3 miles is roughly 5 km, 5 miles roughly 8 km, 8 miles roughly 13 km. The error stays under half a percent, which is better than most mental shortcuts.
Why does the UK still use miles?
Road signage was never converted, largely because of the cost of replacing every sign and the safety risk of a transition period. Distances and speeds stayed imperial while almost everything else went metric, which is why fuel is sold in litres but economy is quoted per gallon.