Miles to Kilometres

About the mile and the kilometre

The international mile was fixed at exactly 1,609.344 metres in 1959, when the United States, the United Kingdom and the Commonwealth countries agreed to define the yard as 0.9144 m. The kilometre is 1,000 metres, a multiple of the SI base unit of length. Road signs in the US and UK use miles; almost everywhere else uses kilometres, so this conversion comes up for travel, running and car specifications.

The US survey mile, still found in some older land records, differs from the international mile by about 3 mm per mile and is not used here.

Worked example

A 26.2-mile marathon: 26.2 × 1.609344 = 42.1648128 km. The official marathon distance is defined as 42.195 km, which is 26.2188 mi, so "26.2" is itself a rounded figure.

Reverse

To go from kilometres to miles, divide by 1.609344 (or multiply by about 0.621371). The swap button takes you to the kilometres to miles page.

The page multiplies by the exact factor:

km = mi × 1.609344

The factor follows from 1 mi = 1,760 yd and 1 yd = 0.9144 m, both exact by definition, so the result is exact to the precision of the number you type. Floating-point noise beyond 15 significant digits is removed, and the display is rounded to the precision you choose (6 significant figures by default). Copy result always copies the full value.