Convert Miles to Kilometers

The formula

To convert miles to kilometers, multiply by 1.609344:

km = miles × 1.609344

• km — the result in kilometers.
• miles — the input distance in statute miles.
• 1.609344 — the exact SI-defined conversion factor. 1 mile = 1,609.344 m = 1.609344 km by the 1959 international agreement.

The reverse: to convert km to miles, multiply by 0.621371 (see the KM to Miles calculator).

Worked example

Using the default input of 10 miles:

1. Multiply by 1.609344: 10 × 1.609344 = 16.09344.
2. Round: 16.093 km.

So 10 miles = 16.093 km. As a rough check: 10 × 1.6 = 16, which is close enough for everyday use.

Miles to km reference table

Miles	Kilometers
1 mi	1.6093 km
5 mi	8.0467 km
10 mi	16.093 km
13.1 mi	21.082 km (half marathon)
25 mi	40.234 km
26.2 mi	42.165 km (marathon)
50 mi	80.467 km
60 mi	96.561 km
100 mi	160.93 km
200 mi	321.87 km
500 mi	804.67 km

History & standards

The statute mile originates from the Roman mille passuum (1,000 double paces, about 1,480 m). Queen Elizabeth I redefined it as 8 furlongs = 5,280 feet in 1593. The 1959 International Yard and Pound Agreement then fixed the foot at exactly 0.3048 m, making 1 mile = 1,609.344 m — an exact, legally binding definition used worldwide today.

The kilometre is an SI unit: 1,000 metres, where the metre has been defined since 1983 as the distance light travels in vacuum in 1/299,792,458 second. This physical definition makes the metre — and hence the km — more stable and universally reproducible than any physical artefact.

Common applications

• Running & cycling. US race distances (5-mile, 10-mile, half marathon) need km conversions for international comparisons or GPS apps set to metric.
• Driving abroad. UK road signs show miles; European signs show km. Converting before a cross-Channel trip prevents range anxiety on unfamiliar roads.
• Fuel economy. Miles per gallon (mpg) uses miles; l/100 km uses km. Converting the distance figure is the first step in comparing fuel efficiency between systems.
• Aviation & maps. Great-circle distances between airports are often given in statute miles; converting to km aligns them with ICAO standards.

Limitations & gotchas

• This calculator converts statute miles. A nautical mile = 1.852 km exactly and is not interchangeable with a statute mile (1.609344 km).
• The exact factor is 1.609344 — a terminating decimal, which is unusual for unit conversions. This makes the miles-to-metres calculation one of the few exact cross-system conversions.
• Historical “miles” in different countries (Scottish mile, Irish mile, German Meile) differ from the modern statute mile. Always verify which “mile” a historical source uses.

Sources & references

• BIPM, “The International System of Units (SI), 9th edition” (2019).
• NIST Special Publication 330 (2019).
• 1959 International Yard and Pound Agreement, Federal Register.