The conversion
The mile is 1,760 yards, and because the yard is defined as exactly 0.9144 m, the mile comes out at exactly 1,609.344 m. No approximation involved:
Type in either box above and the other fills in as you type. The same factor works for speeds, because "per hour" is unchanged on both sides: 70 mph is 112.65 km/h.
Worked examples
Running distances
Race distances are where the two systems collide hardest: British events are measured in kilometres, but pace, tradition and the marathon's famous "26.2" are all imperial. These are the figures worth memorising.
- 5K (parkrun) = 3.11 miles
- 10K = 6.21 miles
- 10 miles = 16.09 km
- Half marathon = 21.0975 km = 13.11 miles ("13.1")
- Marathon = 42.195 km = 26.22 miles ("26.2")
- 50K ultra = 31.07 miles
Miles at home, kilometres everywhere else
The UK signs its roads in miles and its runs in kilometres, which is why this conversion never goes away. Drive off the ferry into France and the limits switch to km/h (130 on the motorway is about 81 mph); enter a race and the distance is a 5K or 10K even though your training app may log miles. Runners flipping between the two can lean on a simple pace anchor: a 5 minute per km pace is almost exactly 8 minutes per mile, because one mile is about 1.6 km.
For rough mental conversion, multiply miles by 8 and divide by 5 to get kilometres, and do the reverse to come back: 50 miles is about 80 km. The shortcut is accurate to within half a percent, which is plenty for road signs. When you need the precise figure, the exact factor is 1.609344, and this page uses nothing else.
Pace, the runner's version of speed, converts the opposite way round to distance: minutes per mile are longer than minutes per kilometre, by the same 1.609 factor. A 10 minute mile is about 6 minutes 13 seconds per kilometre, and a 6 minute kilometre is about 9 minutes 39 seconds per mile. Most running watches will display either, but race pacing charts and the kilometre markers on a British course tend to commit to one system, so it pays to know your target pace in both before the gun goes.
One quiet exception: the nautical mile used at sea and in the air is a different unit entirely, 1.852 km, so a knot (one nautical mile per hour) is about 1.15 mph. For every other everyday unit, metres, yards, feet and the rest, our length converter covers the full set, and if it is fuel economy you are converting, the MPG converter translates mpg into litres per 100 km.
Frequently asked questions
How many kilometres are in a mile?
Exactly 1.609344 km. The mile is defined as 1,760 yards and the yard as exactly 0.9144 m, which fixes the mile at 1,609.344 m. For quick mental maths, a mile is about 1.6 km and a kilometre is about 0.62 miles.
How many miles is a 5K or 10K?
A 5K is 3.11 miles and a 10K is 6.21 miles. Divide the kilometres by 1.609344 to get miles. Parkrun's 5 km course is why many British runners think in kilometres even though road signs use miles.
How long is a marathon in miles and km?
A marathon is 42.195 km, which is 26.22 miles, usually quoted as 26.2. A half marathon is 21.0975 km, or 13.11 miles, usually quoted as 13.1.
How do I convert km to miles in my head?
Multiply by 0.6, or slightly better, multiply by 5 and divide by 8. So 80 km is about 50 miles. Going the other way, multiply miles by 8 and divide by 5: 50 miles is about 80 km. The exact factor is 1.609344.
Is 70 mph the same as 113 km/h?
Very nearly. 70 × 1.609344 = 112.65 km/h, so the UK motorway limit is just under 113 km/h. Speed converts with the same factor as distance because the time part (per hour) does not change.