Kilometres to Miles
Convert kilometres to miles with the exact defined factor.
The arithmetic happens in this page. Nothing you type is sent anywhere.
A kilometre is 0.621371 miles, so the quick mental version is to take about five eighths, or multiply by six and move the decimal. That gets you close enough to read a road sign; it is not close enough to price a shipment or plan fuel.
More about Kilometres to Miles
The conversion matters most to people moving between systems rather than living in one. A driver in Britain reading a European sat-nav, a runner comparing a 10K against a six-mile route, an engineer reading a datasheet written on the other side of an ocean. In each case the number arrives in the wrong unit at the moment it has to be acted on.
The factor is exact rather than approximate. A mile is 1609.344 metres by definition, because an inch was fixed at exactly 25.4 millimetres in 1959 and everything imperial follows from it. Converters that use 1.609 or 1.61 are wrong in the fourth digit, which is invisible over a kilometre and about ten metres over a marathon.
Useful markers worth remembering: 5 km is 3.11 miles, 10 km is 6.21, a half marathon is 13.1 miles and a full one 26.2. A 100 km/h speed limit is 62 mph, and 50 km/h is 31 mph.
- Exact factor: one mile is 1609.344 metres by definition
- Both directions from the same page, with a swap button
- Every other length unit shown underneath, from millimetres to nautical miles
- Common race and speed-limit markers given in the text
- Results grouped the way your language writes numbers
How to use it
- 1Type the number of kilometres you have.
- 2Read the answer in miles as it updates.
- 3Use the swap button if you need to go the other way.
- 4Take any other unit, such as metres or yards, from the table below.
Questions
How many miles is 1 km?
0.621371 miles. Five kilometres is 3.11 miles and ten is 6.21.
What is the quick way to do this in my head?
Take five eighths of the number, or halve it and add a tenth of the original. Both land within a couple of percent, which is fine for a road sign.
Is a 10K race ten miles?
No, it is 6.21 miles. A ten-mile race is 16.1 km, which is a noticeably longer run.
What is 100 km/h in mph?
62 mph. The speed conversion uses the same factor as distance, since an hour is an hour in both systems.
Why do some converters give slightly different answers?
Because they round the factor to 1.609 or 1.61 instead of using the defined 1.609344. The gap is about ten metres over a marathon.