Miles to Kilometers

1 mile = exactly 1.609344 kilometers — an exact international definition established in 1959 and confirmed in NIST SP 811. Type a distance in either unit and the other updates instantly. Click either result to use it as the input.

The formula

km = miles × 1.609344
miles = km ÷ 1.609344  (= km × 0.621371…)

Both conversion factors are derived from the international definition: 1 inch = 25.4 mm (exact), therefore 1 mile = 5280 × 12 × 25.4 mm = 1,609,344 mm = 1.609344 km (exact).

Practical examples

Example 1 — Road trip distance

A US road atlas shows 250 miles between two cities. In km for a European passenger:

250 × 1.609344 = 402.3 km

Example 2 — Speed limit sign

A UK motorway speed limit of 70 mph converted to km/h:

70 × 1.609344 = 112.7 km/h

(Miles per hour and kilometers per hour use the same factor — the per-hour cancels.)

Example 3 — Running race

A 10 km race in miles:

10 ÷ 1.609344 = 6.214 miles

A half marathon is 13.109 miles (21.0975 km). A marathon is 26.219 miles (42.195 km).

Common mistakes

Using 1.6 instead of 1.609344. The approximation introduces a 0.58% error. Over 100 miles that is 0.58 km — small but significant for navigation. The exact factor is 1.609344.

Confusing statute miles with nautical miles. 1 nautical mile = 1852 meters = 1.852 km — larger than a statute mile (1.609344 km). Navigation apps and marine charts use nautical miles; road signs use statute miles.

Applying the factor to area incorrectly. 1 square mile = 1.609344² = 2.59 km². Area conversion requires squaring the linear factor.

International and regional variations

Quick reference — common driving distances