Free Km to Miles Converter — Exact Factor 1.609344

What is a kilometer, and what is a mile?

The kilometer is 1,000 meters — the everyday unit for road distances, race courses and speed limits (km/h) across Europe and almost everywhere else in the world. A kilometer is a 10 to 12 minute walk for most people, and motorway distances between European cities are quoted in kilometers on every road sign. Because it is built on the meter, the kilometer is part of the International System of Units (SI).

The mile used on roads is the statute or international mile: 5,280 feet, defined since the International Yard and Pound Agreement of 1959 as exactly 1,609.344 meters. The word comes from the Roman mille passus, a thousand paces. Miles remain the unit for road distances and speed limits in the United States and the United Kingdom, so anyone driving, running or cycling across the Atlantic meets both units constantly.

How to use the converter

1. Type a distance in the Kilometers box — decimals are welcome, so 21.0975 works for a half marathon. The miles result appears instantly.
2. Or type in the Miles box instead: the converter works both ways, so the kilometers value updates at once.
3. Use the Swap button to reverse the direction. The converted value carries over as the new starting number.
4. Read the result line under the boxes: it shows the full conversion plus the one-unit rate, 1 kilometer = 0.62137 miles.

Km to miles formula

This converter divides by the exact 1.609344 rather than multiplying by the rounded 0.621371, so converting there and back returns the number you started with. The two methods agree to 6 decimals; the division is the exact one.

Worked example

You sign up for a 10K race in Paris. How far is that in miles?

Try both numbers in the converter above — and type 6.21371 in the miles box to watch it return 10 kilometers.

Km to miles conversion table

All values divide by the exact factor 1.609344 and are rounded to 5 decimal places.

Race distances and road trips

• 5K run — 5 kilometers = %5/1.609344:5% miles.
• 10K run — 10 kilometers = 6.21371 miles.
• Half marathon — 21.0975 kilometers = %21.0975/1.609344:5% miles.
• Marathon — 42.195 kilometers = %42.195/1.609344:5% miles.
• City speed limit — 50 km/h = %50/1.609344:5% mph.
• Motorway cruise — 120 km/h = %120/1.609344:5% mph.
• 100-kilometer drive — 100 kilometers = %100/1.609344:5% miles.

Driving abroad and unsure which unit the signs use? Our metric vs imperial conversion guide for Europe covers road signs, speed limits and fuel, country by country.

Frequently asked questions

How many miles is 1 kilometer?

One kilometer is 0.621371 miles (1 ÷ 1.609344 = 0.621371192, shown rounded to 6 decimals). The mile is defined as exactly 1.609344 kilometers, so dividing by 1.609344 gives the exact conversion.

How do I convert km to miles in my head?

Multiply by 0.6 for a quick estimate, or multiply by 5 and divide by 8 for a closer one: 80 kilometers × 5 ÷ 8 = 50 miles, against the exact 49.7097 miles. The 5/8 shortcut is within 0.6 percent, fine for journey planning but not for race timing.

How many miles is 10 kilometers?

10 kilometers is 6.21371 miles (10 ÷ 1.609344 = 6.2137119, rounded to 5 decimals). A 10K race is therefore a little over 6.2 miles.

How many miles is a 42.195-kilometer marathon?

A marathon of 42.195 kilometers is 26.21876 miles (42.195 ÷ 1.609344), usually quoted as 26.2 miles or 26 miles 385 yards.

Is the kilometer to mile conversion exact?

Yes. The international mile is legally defined as exactly 1,609.344 meters, so 1 kilometer equals exactly 1/1.609344 miles. The converter divides by the full exact factor; only the displayed decimals are rounded.

How do I convert km/h to mph?

Use the same factor: divide the km/h figure by 1.609344. For example, 100 km/h ÷ 1.609344 = 62.13712 mph. Speed converts exactly like distance because the hour stays the same on both sides.

Is a nautical mile the same as a mile?

No. A nautical mile is 1.852 kilometers exactly (about 1.1508 statute miles) and is used in sea and air navigation. This converter uses the statute mile of 1.609344 kilometers, the mile on road signs in the United States and the United Kingdom.

Sources

• NIST Special Publication 811, Guide for the Use of the International System of Units (SI) — nist.gov/pml/special-publication-811
• BIPM, The International System of Units (SI Brochure) — bipm.org
• International Yard and Pound Agreement, 1959 — the foot fixed at exactly 0.3048 meters and the international mile at exactly 1.609344 kilometers.

Conversion factors checked against these sources on 14 November 2026.

Disclaimer: conversions divide by the exact factor 1.609344; always follow the speed limit shown on local road signs.

Related tools