Convert km to mi kilometres ↔ miles Free Online Secure
Type a value in kilometres and read it in miles at once. The factor is exact by definition, the arithmetic happens in your browser, and nothing is sent anywhere.
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Common values — Convert km to mi (kilometres ↔ miles)
| km | mi |
|---|---|
| 1 | 0.621371192237 |
| 2 | 1.24274238447 |
| 3 | 1.86411357671 |
| 5 | 3.10685596119 |
| 10 | 6.21371192237 |
| 20 | 12.4274238447 |
| 50 | 31.0685596119 |
| 100 | 62.1371192237 |
Where these units come from
The metre was first defined in 1793 as a ten-millionth of the distance from the equator to the North Pole — a definition nobody could check without surveying a quarter of the planet. It has been redefined four times since, each time to something steadier: a platinum bar, then a prototype kept in Paris, then a wavelength of krypton light, and since 1983 the distance light travels in vacuum in 1/299,792,458 of a second. The inch stopped being a separate thing in 1959, when six countries agreed to define it as exactly 25.4 mm. That agreement is why every conversion on this page between a metric and an imperial length is exact rather than measured: both sides now descend from the same definition.
Where you meet them
Millimetres are the working unit of engineering drawings and of anything made in a workshop; centimetres belong to tailoring, furniture and school rulers; metres to rooms, fabric and running tracks. Feet and inches survive in aviation altitudes worldwide, in American and British construction, and in the diagonal of every screen you have ever bought. Nautical miles are not a quaint survival — one is a minute of latitude, which is why ships and aircraft still navigate in them.
Questions people ask
Which countries still measure road distances in miles?
The United States and the United Kingdom, where road signs show miles, together with a handful of smaller countries such as Liberia and Myanmar. Almost everywhere else road distances are in kilometres. One kilometre is 1000 metres and about 0.621 of a mile, so a distance in miles is about five-eighths of the same distance in kilometres.
Is a mile the same everywhere?
The statute mile on this page is 1609.344 m exactly, which follows from the 1959 inch. The nautical mile is a different unit altogether, 1852 m exactly, defined as one minute of arc along a meridian. The two are not variants of one another and should never be swapped.
Is the answer exact?
Where both units are defined in terms of one another by whole numbers, yes — the page says so above the figure, and the only rounding is in how many digits are shown. Where the ratio has no finite decimal, the page shows twelve significant digits and says the relation is approximate rather than pretending otherwise.
Does anything I type leave my device?
No. The arithmetic runs in your browser; nothing is uploaded and there is no server to upload it to. Load the page once and it keeps working with the network switched off.
A road sign, a race and a rental car: why people convert km to mi
Few conversions are asked for as often as this one. A British motorway sign says 70, a European one says 120, and the difference is not the speed but the unit. A runner who trained for a 10-kilometre race in Berlin signs up for a "6.2-mile" fun run in Boston and wonders whether it is the same distance. A traveller reads that a hotel is "2 km from the beach" and needs to know whether that is a stroll or a taxi ride in a country that thinks in miles. This page exists for exactly those moments. Enter a distance in kilometres and read it in miles at once; the answer comes from the exact definitions of both units, not from a rule of thumb.
The need is older than the internet. Cartographers, sailors, pilots, engineers and teachers have always had to move between the metric system and the imperial and American customary ones, and for a casual user the difficulty is usually not the arithmetic but the doubt: should the number get bigger or smaller, and by how much? In the lines below you will find the factor, worked examples, a short biography of each unit, a comparison, practical situations in which people convert km to mi, and a list of the mistakes that cause trouble.
The sum behind convert km to mi
The factor
One kilometre equals 0.621371 miles, and one mile equals exactly 1.609344 kilometres. To go from kilometres to miles, multiply by 0.621371, or divide by 1.609344 if you prefer to work with the exact number. The second form is the more honest one, because the mile is defined in metres and the 1.609344 is exact; the 0.621371 is only its reciprocal, rounded.
Four worked examples
A 5 km walk is 5 × 0.621371 = 3.107 miles. A 42.195 km marathon is 26.219 miles. A 130 km/h motorway limit is 80.8 mph, which is why German drivers on a 130 stretch seem to hover just above 80. A 7,000 km transatlantic flight is 4,350 miles. Each is the same multiplication, and to convert km to mi a pocket calculator, a phone or the box at the top of this page will do it in a moment.
Doing it in your head
Multiply by 6 and drop a digit: 50 km × 6 = 300, and dropping the last digit gives 30 miles, a little under the exact 31.07. The Fibonacci trick is more accurate: 8 km is about 5 miles, 13 km about 8, 21 km about 13, 34 km about 21. With a little practice you can estimate within two per cent, which is enough for any road trip.
Rounding
Three significant figures are plenty for most travel questions. If your starting number is "about 10 km", an answer of 6.2 miles already says more than the data supports.
The kilometre in plain terms
A thousand metres
The kilometre is a thousand metres, and the metre is, by definition, the distance light travels in a vacuum in 1/299,792,458 of a second. That sounds abstract, but it means every kilometre in the world is the same length, with no regional variants, and that the unit scales by powers of ten. Walk briskly for ten to twelve minutes and you have covered about a kilometre; a cyclist does it in three; a car on a city street in about two.
Where it appears
Road distances, running races, athletics tracks, hiking trails, satellite orbits and the length of a coastline are all quoted in kilometres in most of the world. Car makers print fuel use per hundred kilometres, rail operators measure line length in kilometres, and maps are drawn with a kilometre grid. The symbol is km, written in lower case with a space after the number, and never with a full stop unless it ends a sentence.
The mile, an old measure that stayed
From a thousand paces
The word comes from the Latin mille passus, a thousand double paces of a Roman legionary, which was about 1.48 kilometres. Over the centuries the English mile grew to eight furlongs, and since an international agreement in 1959 the mile used in Britain and the United States has been fixed at exactly 1,609.344 metres, which is why the factor on this page ends so neatly. Until 2023 the United States also kept a survey mile that differs by about two parts per million, which mattered only for land surveys.
Where it appears
The mile survives on the road signs of Britain and the United States, in American speed limits and odometers, in athletics records such as the four-minute mile, and in the fuel consumption figures of cars as miles per gallon. It is an everyday unit for hundreds of millions of people and a puzzle for the rest, and anyone planning a trip there will sooner or later convert km to mi. The symbol is mi, but you will also see "miles" spelled out in running, aviation and road signs.
Kilometre and mile side by side
The mile is the longer unit by a factor of about 1.6, so a distance has fewer miles than kilometres: 100 km is 62.14 mi, while 100 mi is 160.93 km. Think of the kilometre as roughly five eighths of a mile, or the mile as a kilometre and three fifths. The ratio is close to the golden ratio, 1.618, and the Fibonacci sequence provides a curious shortcut: 5 miles is about 8 km, 8 miles about 13 km, 13 miles about 21 km, and so on, accurate to within a per cent or two.
Which should you use? Whichever the reader of your work expects. A scientific paper, a European route description and an airline timetable want kilometres; a US road atlas, a British pub sign and a treadmill in an American gym want miles. For international audiences, give both, with the unit that fits the context first and the other in brackets.
Everyday situations that call for convert km to mi
Driving abroad
A European driving in Britain or the United States meets speed limits in miles per hour and distances in miles, while the car may display kilometres per hour on its speedometer. A 30 mph zone means about 48 km/h, 60 mph is 97 km/h and 70 mph is 113 km/h. Rental cars in the United States show miles on the odometer, and fuel stations quote prices per gallon. Before a long trip, convert the planned legs: a 250-kilometre day is about 155 miles, roughly two and a half hours on a motorway at the American limit of 65 mph.
Running and cycling
Races bridge the two systems daily. A 5K is 3.1 miles, a 10K is 6.2 miles, a half marathon is 21.1 km or 13.1 miles, and the marathon is 42.195 km or 26.2 miles. A runner with a pace of 5 minutes per kilometre is running 8 minutes and 3 seconds per mile. Cyclists reading American route guides, and walkers following long-distance trails such as the Appalachian Trail, with its 2,190 miles, or the Pennine Way, 268 miles, convert to plan daily stages and water.
Travel, maps and trivia
Flight tracking sites, distance charts in guidebooks and hiking maps often come in one unit, and the planner works in the other. The distance from London to Edinburgh is about 645 km by road, 400 miles; from New York to Los Angeles it is about 4,500 km, 2,800 miles. The circumference of the Earth is roughly 40,075 km, or 24,901 miles. Such figures are easy to remember and handy for checking a calculation.
A table for the road
As a rule of thumb for the dashboard: 10 km is 6 mi, 50 km is 31 mi, 100 km is 62 mi, 200 km is 124 mi, 500 km is 311 mi. Memorise two or three anchors and you can sense-check any figure on the page.
How two systems came to share a road
The metre and the revolution
The kilometre is a child of the French Revolution. In the 1790s the National Assembly commissioned a unit of length that belonged to no king, and chose one ten-millionth of the distance from the North Pole to the equator along the meridian through Paris. Two surveyors spent six years measuring the arc between Dunkirk and Barcelona, and the platinum bar they made became the metre. Kilometres followed naturally, a thousand of them. The idea spread across Europe in the nineteenth century, and today almost every country uses it. Anyone who wants to convert km to mi is, in effect, stepping between a revolutionary invention and an ancient custom.
Britain and America hold on
Britain legalised the metric system for trade in 1864 and began metrication in earnest in 1965, but road signs stayed in miles, and in 2009 the government confirmed that they would. The United States passed the Metric Conversion Act in 1975, which made the metric system the preferred system for trade, though not compulsory, and the result is a country of dual labelling: a soft drink in two litres, a road sign in miles, a science class in kilometres. Canada converted its road signs in 1977, Australia in the 1970s, and Ireland changed its signs from miles to kilometres in 2005, the year when many drivers had to unlearn a habit.
The countries that still count in miles
Apart from the United Kingdom and the United States, a handful of territories use miles on the road, among them Liberia and Myanmar in practice, and some Caribbean and Pacific islands with a British or American heritage. In everyday English the word survives in idioms, such as going the extra mile, a mile a minute and miles away, which no metric reform has yet replaced. Sports commentary in several countries still talks about the mile race, the glamorous event of middle-distance running, in which the four-minute barrier was broken by Roger Bannister in 1954.
How distance is actually measured
Wheels, chains and satellites
Before satellites, distances were measured with chains of a known length, with wheels that counted turns and with triangulation from towers and hills. A car odometer works by counting rotations of a wheel of known circumference, which is why it can be wrong by a per cent or two when the tyres are worn or changed to a different size. A satellite receiver measures position from the arrival times of radio signals and computes distance between fixes, which can be far more accurate, though it adds up small errors when the route is winding. The two methods often disagree by a few hundred metres on a long drive, which is a good reason not to treat a decimal on an app as gospel when you convert km to mi.
Race courses and certified distances
A marathon course must be measured by a certified official, who rides a bicycle fitted with a calibrated counter along the shortest path a runner could legally take, and then adds a safety margin of one per cent so that the course can never turn out short. That is why a certified 42.195 km course is, strictly, about 42.2 km, and why a runner's GPS watch often shows 42.4 or 42.5 after the finish, because the runner has weaved around other runners. When you compare your time with a mile record, the two distances are not interchangeable: a 5K is not exactly 3 miles, and a faster mile does not predict a faster kilometre without allowing for fatigue.
Why precision matters, and when it does not
For a holiday plan, one decimal place is plenty. For a technical drawing, a shipping contract or a flight plan, more digits matter, and the exact definition of the mile, 1,609.344 metres, removes any doubt. In engineering, mixed units have caused costly mistakes; the best known is the loss of the Mars Climate Orbiter in 1999, when one team supplied thrust data in pound-force seconds and another expected newton seconds. Distance is easier to confuse than force, but the lesson is the same: write the unit next to every number, and when you convert km to mi copy the unit with the value.
A habit for travellers
When you plan a journey in a country with the other unit, set the navigation app to that country's units, so that signs and instructions agree. Then use this page only for checking totals, because with the right settings you rarely need to convert km to mi by hand; such as the distance of a whole trip or a race, and you will rarely do the arithmetic by hand.
More values for convert km to mi
A longer list of conversions
If the value you need is not in the first list, these further conversions may be close enough to read off directly:
- 0.1 km = 0.0621371 mi
- 0.5 km = 0.310686 mi
- 3 km = 1.86411 mi
- 4 km = 2.48548 mi
- 7 km = 4.3496 mi
- 15 km = 9.32057 mi
- 20 km = 12.4274 mi
- 75 km = 46.6028 mi
- 200 km = 124.274 mi
- 500 km = 310.686 mi
- 2,000 km = 1,242.74 mi
- 10,000 km = 6,213.71 mi
Slips to avoid when you convert km to mi
Dividing instead of multiplying
When you convert km to mi, the result is a smaller number, so multiply by 0.6214 or divide by 1.609. A frequent slip is to multiply by 1.609, which makes a 100 km journey sound like 161 miles. If the answer looks bigger than the starting figure, you have gone the wrong way.
Mixing mph and km/h
Speed limits and speedometers come in both units, and a car rented abroad may show only one. 100 km/h is 62 mph, not 100; 100 mph is 161 km/h. A driver who confuses them either crawls or breaks the law.
Rounding the factor too early
Using 0.6 instead of 0.6214 gives an error of nearly 3 per cent, which adds up over long distances: on a 5,000 km trip it is 100 miles. For a rough sense, 0.6 is fine; for planning fuel or timing, use the full factor.
Quick answers about kilometres and miles
How many miles are in a kilometre?
0.621371 miles, or a little under five eighths. That single number is all you need to convert km to mi.
How many kilometres are in a mile?
Exactly 1.609344 kilometres, so a mile is a kilometre and about three fifths.
What is 10 km in miles?
6.2137 miles, the distance of a standard 10K race. It is the most popular request when people convert km to mi.
What is 100 km in miles?
62.137 miles. A motorway journey of 100 km therefore takes about an hour at 100 km/h, or about an hour at 62 mph.
Is the figure exact?
The relationship is exact by definition; the displayed digits are rounded for readability, so the page is as reliable as any tool you could use to convert km to mi.
Is my number sent anywhere?
No. The calculation runs in your browser and nothing is uploaded.
Related pages and a last word
If you work with distances regularly, these conversions sit close by: Convert km to dm, Convert km to nmi, Convert nmi to mi, Convert ft to mi, Convert mi to nmi, Convert °C to °F, Convert °F to °C, Convert L to gal, Convert gal to L. The reverse of this page is Convert mi to km, which uses the same definitions backwards and returns the number you started with.
In short, to convert km to mi multiply by 0.6214, check that the answer is smaller than the starting figure, and round to the precision of your data. Your number stays on your device: the arithmetic is done locally, with no account and nothing to delete afterwards.