Convert Miles to Kilometers (mi to km)

This direction is for when you already have a distance in miles — a US road sign, a race result, a US car's odometer reading — and need it in kilometers for an international or metric context: comparing against a European map, an official race distance, or a metric fuel-economy figure.

US races are usually described in miles: a 5K is still called a "5K" but is often paced in miles, a 10K is 6.2 miles, a half marathon is 13.1 miles, and a full marathon is 26.2 miles. Converting a US runner's mile pace to a km pace — useful when comparing against international race results published in kilometers — uses this same exact factor: 26.2 miles converts to 42.16 km, very close to the official 42.195 km marathon distance.

US highway speed limits are posted in miles per hour — commonly 55, 65, or 70 mph — which convert to about 88.5, 104.6, and 112.7 km/h. That's worth knowing before driving in the US as a visitor from a km/h-only country, since the identical 1.609344 ratio applies to speed exactly as it does to distance.

Fuel economy is another common trigger: a US car rated at 30 miles per gallon doesn't translate directly to a metric liters-per-100-km figure without first converting the distance component, since the two measures use inverted units (distance per volume vs. volume per distance).

Britain is why this direction still matters inside Europe: road distances and speed limits in the UK are posted in miles and mph, while the Republic of Ireland moved its speed limits to km/h in 2005, so crossing the border changes the unit without changing the road. A 30 mph urban limit is 48.3 km/h and a 70 mph motorway limit is 112.7 km/h. One caution goes with it — the mile converted here is the statute mile, not the nautical mile, which is a separate unit fixed at exactly 1.852 km and used for sea and air navigation.