Miles to Kilometers Converter

One mile is exactly 1.609344 km, and 1 km is about 0.621371 miles

The international mile is 1,760 yards, and since 1 July 1959 the yard has been defined as exactly 0.9144 m. So 1 mi = 1,760 × 0.9144 m = 1,609.344 m, or 1.609344 km. The US National Institute of Standards and Technology (NIST) lists the mile-to-kilometer factor in its conversion tables as the exact value 1.609344, with no rounding. Going from miles to kilometers means multiplying by that number, so the answer always ends in a finite decimal. Going from kilometers to miles means dividing by it, and 1 km = 0.621371192… mi never ends, so those results have to be rounded.

In the converter above, the miles field and the kilometers field follow each other. Whichever one you typed in last is the source, and between the two fields you will see "≈" if the other value was rounded or "=" if it came out exactly. Choose "Speed" and the same ratio converts mph to km/h. Fractions such as 1/4 or 1 1/2 can be typed in as they are. Under the result you also get the same number read in the opposite direction and a nautical-mile value, which is a quick way to catch yourself when you are unsure whether to multiply or divide.

When you need to move between miles and kilometers

• UK and US road signs and speed limits: the Department for Transport guide "Know Your Traffic Signs" says distances to destinations are shown in miles, and that distances under 3 miles may be written as fractions. GOV.UK gives the car speed limits as 30 mph in built-up areas (20 mph in Wales), 60 mph on single carriageways and 70 mph on dual carriageways and motorways. US signs follow the MUTCD, which sets speed limit numbers in steps of 5 mph. If you are reading a hire-car dashboard, or want to turn a sat-nav distance into kilometers, you need the conversion.
• Race distances and running logs: World Athletics sets the marathon at 42.195 km, which is about 26.2 miles. If you are used to miles but sign up for a race measured in kilometers, or share a log with someone who runs in kilometers, you will convert constantly. The World Athletics list of world records also has a separate Mile event.
• Odometers and mileage: a car's history, an ad for a used vehicle or a foreign range figure may be in miles when you need kilometers, or the other way round. A large number such as 100,000 miles is off by hundreds of kilometers if you round the factor to 1.6, so the exact factor matters.
• Travel and reading in kilometers: if you are in the US or UK and read a source that gives kilometers, such as a race course, a trail length abroad or a distance between two cities, you have to turn it back into miles. The same goes for the reverse when a guide abroad gives only miles. If the distance is at sea or in the air it may be nautical miles rather than statute miles, so read the "Common mistakes" section first.

How to use it

1. Pick "Distance" to convert miles and kilometers, or "Speed" to convert mph and km/h. The factor is the same in both modes. Only the unit labels change.
2. Type a value you know into the miles field or the kilometers field. Thousands separators such as 1,234.5 are fine, and so are fractions such as 1/4 or 1 1/2.
3. Choose the number of decimals (0, 1, 2, 4 or 6) and the fields, the dial and the common values all round to that. The result sentence shows the whole exact value if it ends, and at least six decimals if it does not (up to 10 significant digits when the whole-number part is long).
4. On the two-scale dial the outer scale is miles and the inner scale is kilometers. One needle points at both, so you can see how the same distance reads in each unit.
5. The mental estimate panel shows the result of two methods you can do without a calculator, along with a bar showing how far each is above or below the exact value.
6. Tap a common value to drop it into the field above. "Copy result" copies the result sentence, and "Copy link" copies a web address that contains your current value.

How the calculation works

1. Miles to kilometers: miles × 1.609344. For example 26.2 mi × 1.609344 = 42.1648128 km.
2. Kilometers to miles: kilometers ÷ 1.609344, which is the same as multiplying by 0.621371192…. For example 10 km ÷ 1.609344 = 6.213711922…, which rounds to 6.2137 mi at four decimals.
3. Why the factor is 1.609344: a mile is 1,760 yards (5,280 feet) and a yard is exactly 0.9144 m. Multiply 1,760 × 0.9144 and you get 1,609.344 m, so 1 mi = 1.609344 km.
4. Speed: mph and km/h are both "per hour", so the distance factor carries over unchanged. 60 mph × 1.609344 = 96.56064 km/h, and 100 km/h ÷ 1.609344 = 62.137119… mph.
5. Fractions: 1/4 mi is 0.25 × 1.609344 = 0.402336 km (402.336 m). 1 1/2 mi is 1.5 × 1.609344 = 2.414016 km.
6. Rounding: the converter works out the exact value as a fraction first and then rounds half up to the number of decimals you chose. If the whole-number part is long it trims the decimals so only 10 significant digits show, and if a value above zero would display as 0 it adds places until three significant digits appear.

Common distances

Odometer-sized numbers use the same factor: 10,000 miles is 16,093.44 km, 50,000 miles is 80,467.2 km, 100,000 miles is 160,934.4 km and 150,000 miles is 241,401.6 km.

mph and km/h speed tables

The GOV.UK speed limits page prints 48 km/h after 30 mph, 96 km/h after 60 mph and 112 km/h after 70 mph in brackets. Those are rounded-down figures. The exact conversions are 48.28032 km/h, 96.56064 km/h and 112.65408 km/h.

Race distances and pace

Pace (the time it takes to cover one unit of distance) converts in the opposite direction to distance. A mile is longer than a kilometer, so a pace per mile is the pace per kilometer multiplied by 1.609344, and a pace per kilometer is the pace per mile divided by 1.609344. The table below is rounded to the nearest second.

To work out a pace from a distance and a finishing time, or to find the pace that fits a goal time, use the running pace calculator.

Estimating in your head

Miles to km: multiply by 1.6. You can do 1.6 as "the number, plus half of it, plus a tenth of it". For 10 mi that is 10 + 5 + 1 = 16 km, which is about 0.58% under the exact 16.09344 km. Because 1.6 is slightly smaller than 1.609344, the error is the same percentage (−0.58%) whatever number you start with.

Km to miles: take half, then add a tenth. That is the same as multiplying by 0.6, so 10 km becomes 5 + 1 = 6 mi. The exact figure is 6.2137 mi, so this runs about 3.44% low. For a closer answer divide by 8 and multiply by 5 (× 0.625): 40 km ÷ 8 × 5 = 25 mi, against an exact 24.8548 mi, which is about 0.58% high.

The Fibonacci shortcut is another way. The Fibonacci numbers (1, 2, 3, 5, 8, 13, 21, 34, 55, 89, each the sum of the two before) have neighbors whose ratio approaches the golden ratio φ = 1.6180339887…. That is only about 0.54% away from 1.609344, so replacing a number of miles with the next Fibonacci number gives a kilometer estimate (5 mi ≈ 8 km, 8 mi ≈ 13 km, 13 mi ≈ 21 km). For a number that is not a Fibonacci number, split it into Fibonacci numbers that are not neighbors, and shift each one up. Every positive whole number can be written as such a sum in exactly one way (the Zeckendorf representation). 26 mi = 21 + 5, which becomes 34 + 8 = 42 km, about 0.38% above the exact 41.842944 km. To go from kilometers to miles, shift each part down one step instead.

As the table shows, the Fibonacci estimate is rough for small numbers and settles near +0.54% as the numbers grow. The converter's mental estimate panel reduces that error for small numbers by treating values under 10 in steps of 0.1 (so 5.5 becomes 55) and values of 1,000 or more by their first three digits, then moving the decimal point back afterwards.

Common mistakes

• Multiplying when you should divide: multiply 10 km by 1.609344 and you get 16.09, which is the answer for 10 miles. For the same distance, the number in kilometers is always bigger than the number in miles. The "Read the other way" line under the result shows the same number converted in the opposite direction, so you can compare the two.
• Reading nautical miles as miles: a nautical mile (NM) is exactly 1.852 km, about 1.1508 times the international mile. Treat a ship's or aircraft's distance, or a speed in knots (kn), as statute miles and you will be nearly 15% out.
• Rounding big distances to 1.6: 100,000 miles × 1.6 is 160,000 km, but the exact figure is 160,934.4 km, a difference of 934.4 km. Use 1.609344 for anything you plan to record.
• Applying a length factor once to an area: a square mile needs the length factor twice, so 1 sq mi = 1.609344² = 2.589988110336 km². Multiply by 1.609344 only once and the area comes out far too small.
• Mixing in the US survey mile: the mile in older US survey data is based on the survey foot and equals 1.609347 km, which is about 3.2 mm longer per mile than the international mile. Under the US decision published by NIST, 31 December 2022 was the last day to use the survey foot, and from 1 January 2023 the international foot (0.3048 m) replaces it.

Limits

• Only the international mile (1.609344 km) and the nautical mile (1.852 km) are calculated. Survey miles and the old regional miles that differed from place to place are not covered.
• Results are rounded to the decimals you picked, and values with a long whole-number part show only 10 significant digits. For the full value, check the result sentence and the formula.
• The mental estimates are rough values to give you a feel for the size. For contracts, records and official forms, write the exact value together with the original unit.
• You can enter values from 0 up to 1 billion, in the unit you typed.
• Your input is calculated in your own browser and is not sent anywhere. If you press "Copy link", the value goes into the web address.

Basis: the mile and nautical mile factors are the defined values in NIST SP 811 B.8, so they do not change from year to year. The UK speed limits and road signs, the US speed limit sign rules, the World Athletics rules and world records list, and the mathematical definitions were checked against the original sources on 2026-10-20.

Sources

• 01NIST SP 811 Appendix B.8 — Factors for units listed alphabeticallymile 1.609 344 km, mile per hour 1.609 344 km/h, mile (nautical) 1 852 m (exact), mile (U.S. survey) 1.609 347 km. Checked 2026-10-20
• 02NIST — SI Units: LengthThe yard of 0.9144 m from 1 July 1959, giving 1 in = 25.4 mm (exact)
• 03NIST — U.S. Survey FootLast used on 31 December 2022, replaced by the international foot from 1 January 2023
• 04GOV.UK — Speed limitsCars: built-up areas 30 mph (48 km/h), 20 mph in Wales; single carriageways 60 mph (96 km/h); dual carriageways and motorways 70 mph (112 km/h)
• 05Department for Transport — Know Your Traffic SignsDistances to destinations are shown in miles; under 3 miles they may be shown as fractions
• 06Department for Transport — Traffic Signs Manual, Chapter 38.2.1 Speed limits are shown in miles per hour (mph)
• 07FHWA MUTCD 11th Edition — Chapter 2BSection 2B.21 Speed limit sign (R2-1) numbers are in multiples of 5 mph
• 08World Athletics — C2.1 Technical RulesRule 55.1 standard road race distances, Marathon (42.195km)
• 09World Athletics — World RecordsThe Mile event in the world records list
• 10Wolfram MathWorld — Golden Ratioφ = (1 + √5)/2 = 1.6180339887…
• 11Wolfram MathWorld — Fibonacci NumberThe ratio of neighboring Fibonacci numbers approaches φ
• 12Wolfram MathWorld — Zeckendorf RepresentationEvery positive integer is a sum of non-neighboring Fibonacci numbers in exactly one way

Frequently asked questions

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