What this does
Turns a distance in kilometers into miles as you type. The factor is a definition, not a measurement: 1 mile = 1.609344 km exactly, so miles = km ÷ 1.609344, which is the same as km × 0.621371. The page opens at 1 km = 0.621371 mi. Edit either box and the other one updates on every keystroke; the ⇄ button swaps the units and keeps the number on the left. Results are rounded to six decimal places. It runs entirely in your browser, so it works offline — handy on a motorway with no signal.
How many miles is a 5K, 10K, half marathon, or marathon?
Race distances are defined in kilometers, which is why the mile figures look odd. A 5K is 3.106856 miles; a 10K is 6.213712 miles. The half marathon is 21.0975 km, which converts to 13.109379 miles, and the full 42.195 km marathon is 26.218757 miles. The familiar "13.1" and "26.2" are just those numbers rounded. If your watch shows pace per kilometer, multiply by 1.609344 to get pace per mile: 4:30 min/km is 4.5 × 1.609344 = 7.24 minutes, or about 7:15 min/mile.
Kilometers to miles at a glance
| Kilometers | Miles | Where you'll see it |
|---|---|---|
| 1 | 0.621371 | the definition |
| 5 | 3.106856 | a 5K |
| 10 | 6.213712 | a 10K |
| 21.0975 | 13.109379 | half marathon |
| 42.195 | 26.218757 | marathon |
| 100 | 62.137119 | a "century" ride, ultra distance |
| 130 | 80.778255 | French and Italian motorway limit (km/h) |
| 400 | 248.548477 | typical EV range on a European listing |
What's a quick way to convert km to miles in my head?
Multiply by 0.6 and nudge up a touch: 50 km → 30, real answer 31. If you want it tighter, halve the number and add a quarter of that: 80 km → 40 + 10 = 50 (real 49.7). There's also the Fibonacci trick — consecutive Fibonacci numbers sit in almost exactly this ratio, so 8 km ≈ 5 mi, 13 km ≈ 8 mi, 21 km ≈ 13 mi, 34 km ≈ 21 mi. It works because the golden ratio (1.618) is within half a percent of 1.609.
How do I read km/h speed limits in mph?
Speed uses the same factor, since it's just distance per hour. Divide km/h by 1.609344: a 50 km/h town limit is 31 mph, 80 km/h is 50 mph, 100 km/h is 62 mph, 120 km/h is 75 mph, and the 130 km/h on a French autoroute is 81 mph. Most hire-car speedometers show both scales, but the small inner ring is easy to misread — if in doubt, remember that 100 km/h is a hair over 60 mph. The full converter has a dedicated Speed tab with knots and m/s as well.
Why is a mile exactly 1.609344 km?
In 1959 the US, UK, Canada, Australia, New Zealand and South Africa agreed to define the international yard as exactly 0.9144 m. A mile is 1,760 yards, and 1,760 × 0.9144 = 1,609.344 m. That's why the tool's arithmetic has no rounding error of its own — the only rounding is the six-decimal display. Worked example: your sat-nav says 340 km to go; 340 ÷ 1.609344 = 211.2662046…, which the tool shows as 211.266205 miles.
Can I convert miles to km on this page too?
Yes — either type in the right-hand (miles) box and the kilometers recompute, or press ⇄ to flip the units. The dropdowns still list every length unit, so you can switch to meters, yards, or nautical miles without leaving the page. For the other direction with its own explainer, see miles to km.