Short answer
- One kilometer is 0.621371 miles, and one mile is exactly 1.609344 kilometers. To convert kilometers to miles, multiply by 0.621371. To convert miles to kilometers, multiply by 1.609344. So 5 kilometers is 3.11 miles, 10 kilometers is 6.21 miles, 100 kilometers is 62.14 miles, and 100 miles is 160.93 kilometers. For speed, the same factors apply to the numbers because the hour stays the same on both sides: 100 kilometers per hour is 62.14 miles per hour, and 60 miles per hour is 96.56 kilometers per hour. The mile figure is always the smaller number for the same distance, because a mile is longer than a kilometer. If a conversion ever gives you more miles than kilometers, the wrong factor was used.
By Emma Hudson
Kilometers and miles measure the same thing, distance, but they belong to different systems, and mixing them up can turn a short run into a long one or a speed limit into a fine. This guide gives the exact conversion in both directions, full tables you can check at a glance, the race and road distances people ask about most, and a separate, careful treatment of speed, because converting a distance and converting a speed are related but not the same job.
What a Kilometer and a Mile Actually Are
A kilometer is a metric unit built on the meter, the base unit of length in the International System of Units. The prefix kilo means one thousand, so one kilometer is exactly 1,000 meters. That simple decimal structure is why metric distances scale so cleanly: 10 kilometers is 10,000 meters, and half a kilometer is 500 meters, with no irregular steps in between.
A mile is a unit from the imperial and United States customary systems. The international mile used for road distances, running races, and maps in the United States and the United Kingdom is 5,280 feet, or 1,760 yards. Since 1959, the yard has been defined as exactly 0.9144 meters under the international yard and pound agreement, and the foot as exactly 0.3048 meters. Multiply 5,280 feet by 0.3048 meters per foot and the result is exactly 1,609.344 meters, which is 1.609344 kilometers. That is why the mile to kilometer factor is not a rough measurement that might change with a better ruler. It is exact by definition, fixed by the definitions of the foot and the meter themselves.
Because both units are defined against the meter, the conversion between them never drifts. Every figure in this article follows from that one exact relationship, and every table value has been recomputed from it.
One other mile is worth knowing about. The nautical mile, used in sea and air navigation, is exactly 1,852 meters, or 1.852 kilometers, about 1.15 times as long as the statute mile. If a distance comes from a chart, a flight, or a boat, check whether it is given in nautical miles before converting it as if it were a road distance.
The Two Formulas, and Why They Are Reciprocals
The whole conversion rests on two multiplication formulas:
| Direction | Formula |
|---|---|
| Kilometers to miles | Miles = kilometers x 0.621371 |
| Miles to kilometers | Kilometers = miles x 1.609344 |
The two factors are reciprocals of each other. Divide 1 by 1.609344 and the result is 0.621371 when rounded to six decimal places. That is not a coincidence to memorize; it is what has to happen whenever two units measure the same quantity. Going from the smaller unit to the larger unit must shrink the number, and going back must restore it, so the two factors multiply together to give 1, apart from rounding.
This also explains which factor is larger. A mile is longer than a kilometer, so any given distance contains fewer miles than kilometers. Converting kilometers into the longer unit uses the smaller factor, 0.621371, and the answer goes down. Converting miles into the shorter unit uses the larger factor, 1.609344, and the answer goes up. Keeping that picture in mind, that miles are longer so the mile count is always smaller, catches most conversion errors before they matter.
For quick estimates, rounded factors are fine: 1 kilometer is about 0.62 miles, and 1 mile is about 1.6 kilometers. Use the rounded versions for planning a walk or judging a journey. Use the full factors for a race distance, a speed limit, a fuel calculation, or anything that will be quoted, recorded, or acted on by someone else.
Kilometers to Miles: Method and Worked Examples
The question how many miles in a km has a one line answer: 0.621371 miles. To convert any distance given in kilometers, multiply the number of kilometers by that factor, then round the answer to a sensible number of decimal places. Two decimal places suit almost every everyday purpose, because the distances themselves are rarely known more precisely than that.
Worked example, 1 kilometer: 1 x 0.621371 = 0.621371 miles, which rounds to 0.62 miles. A single kilometer is a little over three fifths of a mile.
Worked example, 5 kilometers: 5 x 0.621371 = 3.106855 miles, which rounds to 3.11 miles. This is the 5K race distance covered in more detail below.
Worked example, 10 kilometers: 10 x 0.621371 = 6.21371 miles, which rounds to 6.21 miles. Notice that doubling the 5 kilometer answer gives 6.22 miles if you double the rounded figure, but 6.21 miles if you convert 10 kilometers directly. That tiny difference is rounding, not an error, and it is why precise work should always convert the original figure rather than doubling a rounded one.
Kilometers to miles table
Every value below was recomputed by multiplying the kilometer figure by 0.621371 and rounding to two decimal places.
| Kilometers | Miles |
|---|---|
| 1 km | 0.62 miles |
| 2 km | 1.24 miles |
| 3 km | 1.86 miles |
| 5 km | 3.11 miles |
| 8 km | 4.97 miles |
| 10 km | 6.21 miles |
| 15 km | 9.32 miles |
| 20 km | 12.43 miles |
| 25 km | 15.53 miles |
| 30 km | 18.64 miles |
| 40 km | 24.85 miles |
| 42.195 km | 26.22 miles |
| 50 km | 31.07 miles |
| 75 km | 46.60 miles |
| 100 km | 62.14 miles |
| 150 km | 93.21 miles |
| 200 km | 124.27 miles |
| 500 km | 310.69 miles |
| 1,000 km | 621.37 miles |
The table checks against itself, which is a good habit with any conversion table. The 200 kilometer figure, 124.27 miles, is twice the 100 kilometer figure of 62.14 miles, apart from a rounding difference in the last digit, and the 1,000 kilometer figure is ten times the 100 kilometer figure on the same terms. A table that scales cleanly like this is a table whose factor was applied consistently.
Miles to Kilometers: Method and Worked Examples
The question how many km are in a mile also has a one line answer: 1.609344 kilometers, exactly. To convert any distance given in miles, multiply the number of miles by 1.609344, then round. Because this factor is exact, answers converted with it are as precise as the rounding you choose at the end.
Worked example, 1 mile: 1 x 1.609344 = 1.609344 kilometers, which rounds to 1.61 km. This is the comparison behind the search phrase 1 mile to 1 km. It is not a conversion of one unit into the other so much as a side by side comparison: a mile, at 1.61 km, is substantially longer than a kilometer, at 0.62 miles. The mile is about 61 percent longer than the kilometer.
Worked example, 10 miles: 10 x 1.609344 = 16.09344 kilometers, which rounds to 16.09 km.
Worked example, 26.2 miles: 26.2 x 1.609344 = 42.16481 kilometers, which rounds to 42.16 km. That figure sits close to the official marathon distance of 42.195 km, and the small gap is explained below: 26.2 miles is itself a rounded figure, so converting it cannot reproduce the exact marathon distance.
Miles to kilometers table
Every value below was recomputed by multiplying the mile figure by 1.609344 and rounding to two decimal places.
| Miles | Kilometers |
|---|---|
| 1 mile | 1.61 km |
| 2 miles | 3.22 km |
| 3 miles | 4.83 km |
| 5 miles | 8.05 km |
| 8 miles | 12.87 km |
| 10 miles | 16.09 km |
| 13.1 miles | 21.08 km |
| 20 miles | 32.19 km |
| 26.2 miles | 42.16 km |
| 50 miles | 80.47 km |
| 100 miles | 160.93 km |
| 200 miles | 321.87 km |
| 500 miles | 804.67 km |
| 1,000 miles | 1,609.34 km |
Check the 5 mile row by hand: 5 x 1.609344 = 8.04672, which rounds to 8.05 km. And the 100 mile figure, 160.93 km, is ten times the 10 mile figure of 16.09 km, as it must be. The 13.1 mile row is included because it is the figure runners often quote for a half marathon; the official half marathon distance is 21.0975 km, which converts to 13.11 miles, so 13.1 miles is a rounded label for the race rather than its exact length.
The Distances People Actually Ask About
A handful of specific conversions account for most real questions, including the search phrases in this article’s keyword set. Each one below is worked in full so the method, not just the answer, is on record.
How many miles is 100 kilometers? Multiply 100 x 0.621371 = 62.1371, which rounds to 62.14 miles. One hundred kilometers is a round number in metric countries and a long drive in imperial ones. In race terms it is an ultramarathon distance, a little over two and a third marathons back to back.
The reverse question is just as common on the road. How many kilometers is 100 miles? Multiply 100 x 1.609344 = 160.9344, which rounds to 160.93 km. Set the two 100 answers side by side, 62.14 miles against 160.93 kilometers, and the need to state the unit with the number becomes obvious.
The phrase 1 mile on km is a search style way of asking what one mile measures in kilometers. The answer is 1.609344 km, or 1.61 km rounded. The same reading applies to any similar phrase: miles to kilometers means multiply by 1.609344, and kilometers to miles means multiply by 0.621371. Confusing the two is the one error that produces a wildly wrong answer, such as reporting a 10 km run as 16.09 miles instead of 6.21 miles.
A quick sanity check works for every conversion. For the same distance, the kilometer figure is always larger than the mile figure. If a conversion breaks that rule, the wrong factor was used, and the calculation should be done again with the other one.
Race Distances: 5K, 10K, Half Marathon, and Marathon
Running is where kilometer and mile figures meet most often, because races are usually named and measured in kilometers while many runners, especially in the United States, think and train in miles.
A 5K is 5 kilometers: 5 x 0.621371 = 3.106855, or 3.11 miles. It is the distance of the weekly 5 kilometer community runs held in parks, and 3.11 miles is the figure to use in a mile based training plan or when comparing a 5K time with a mile based result.
A 10K is 10 kilometers: 10 x 0.621371 = 6.21371, or 6.21 miles. The pair is worth memorizing: 5K is 3.11 miles, 10K is 6.21 miles.
A half marathon is 21.0975 kilometers, exactly half the marathon distance: 21.0975 x 0.621371 = 13.1094, or 13.11 miles. It is usually quoted as 13.1 miles, which is a rounding of 13.11, not a separate distance. Converting 13.1 miles back gives 21.08 km, slightly short of the official 21.0975 km, for the same rounding reason seen with the full marathon below.
A marathon is 42.195 kilometers. Multiply 42.195 x 0.621371 = 26.2188, which rounds to 26.22 miles and is usually quoted as 26.2 miles. The fuller imperial form of the same distance is 26 miles 385 yards. So when a marathon is described as 26.2 miles, that is a convenient rounding of 26.22 miles, which is itself the conversion of the official 42.195 km. Anyone measuring a course, checking a qualifying time, or comparing records should work from 42.195 km, the official figure, and treat 26.2 miles as a label.
Longer standard distances follow the same arithmetic. A 50 kilometer ultramarathon is 50 x 0.621371 = 31.07 miles, and a 100 kilometer race is 62.14 miles. At these lengths the gap between the systems stops being a rounding matter: a runner who mistook 50 km for 50 miles would be planning for a race more than half as long again as the one they entered.
Pace: The Conversion That Runs the Other Way
Pace is where otherwise careful runners get caught, because pace is not a distance. Pace is a time divided by a distance, usually minutes per kilometer or minutes per mile, and converting it uses the factors in the opposite direction from the one intuition suggests.
Here is the reasoning. A mile is longer than a kilometer, so covering a mile at the same speed takes more time than covering a kilometer. A pace figure in minutes per mile must therefore be larger than the same speed expressed in minutes per kilometer. To convert minutes per kilometer into minutes per mile, multiply by 1.609344, the mile to kilometer factor. To convert minutes per mile into minutes per kilometer, divide by 1.609344, or multiply by 0.621371.
Worked example: a pace of 5 minutes per kilometer. Multiply 5 x 1.609344 = 8.04672 minutes per mile, which is 8 minutes and about 3 seconds per mile, written as about 8:03 per mile. Worked example in the other direction: a pace of 10 minutes per mile. Multiply 10 x 0.621371 = 6.21371 minutes per kilometer, which is about 6:13 per kilometer.
| Pace per kilometer | Same pace per mile |
|---|---|
| 4:00 per km | about 6:26 per mile |
| 5:00 per km | about 8:03 per mile |
| 6:00 per km | about 9:39 per mile |
| 7:00 per km | about 11:16 per mile |
Each row was recomputed by multiplying the minutes per kilometer figure, expressed in decimal minutes, by 1.609344 and converting the decimal part back into seconds. The lesson generalizes: whenever a rate has distance in its denominator, the conversion factor flips. Distance itself never flips. A kilometer is still 0.621371 miles, on a road sign or inside a pace figure.
Speed: Kilometers per Hour and Miles per Hour
Speed needs its own section because it is the conversion with legal consequences, and because it must not be muddled with the distance conversion even though it uses the same numbers. Speed is a distance divided by a time. A speed in kilometers per hour and a speed in miles per hour share the same time unit, the hour, so the hour cancels out of the conversion and only the distance part changes. That is why the same two factors apply to the speed numbers themselves:
| Direction | Formula |
|---|---|
| Kilometers per hour to miles per hour | mph = km/h x 0.621371 |
| Miles per hour to kilometers per hour | km/h = mph x 1.609344 |
Worked example: 100 km/h. Multiply 100 x 0.621371 = 62.1371, or 62.14 mph. A car traveling at 100 km/h is traveling at about 62 mph, not at 100 mph, and the difference is large enough to matter for both safety and the law. Worked example in the other direction: 60 mph. Multiply 60 x 1.609344 = 96.5606, or 96.56 km/h.
Speed limit table, kilometers per hour to miles per hour
| Speed in km/h | Speed in mph |
|---|---|
| 30 km/h | 18.64 mph |
| 50 km/h | 31.07 mph |
| 60 km/h | 37.28 mph |
| 80 km/h | 49.71 mph |
| 90 km/h | 55.92 mph |
| 100 km/h | 62.14 mph |
| 110 km/h | 68.35 mph |
| 120 km/h | 74.56 mph |
| 130 km/h | 80.78 mph |
Speed limit table, miles per hour to kilometers per hour
| Speed in mph | Speed in km/h |
|---|---|
| 20 mph | 32.19 km/h |
| 25 mph | 40.23 km/h |
| 30 mph | 48.28 km/h |
| 40 mph | 64.37 km/h |
| 50 mph | 80.47 km/h |
| 60 mph | 96.56 km/h |
| 65 mph | 104.61 km/h |
| 70 mph | 112.65 km/h |
| 75 mph | 120.70 km/h |
| 80 mph | 128.75 km/h |
Every value in both tables was recomputed from the exact factors and rounded to two decimal places. Read them with the driving situation in mind. A driver used to miles per hour who sees a 50 sign in a kilometers per hour country is looking at a limit of about 31 mph, a typical town speed at home. A driver used to kilometers per hour who sees a 70 sign in a miles per hour country is looking at about 113 km/h, a motorway speed. The familiar looking number is the trap: a figure on a sign means nothing until its unit is known. Convert the limit before setting off rather than estimating it on the move.
Converting Without a Calculator
Three mental shortcuts, each clearly an approximation, cover most everyday needs. None of them should be used where the answer has a legal, safety, or record keeping consequence; for those, use the full factors above.
First, kilometers to miles: multiply by 0.6, then add a little. For 10 km, 10 x 0.6 = 6.0 miles, against the exact 6.21 miles. The shortcut is short by about 0.02 miles for every kilometer, so adding roughly 0.02 per kilometer improves it: for 10 km, 6.0 plus 0.2 gives 6.2 miles, close enough to judge a journey.
Second, miles to kilometers: multiply by 1.6. For 10 miles, 10 x 1.6 = 16.0 km, against the exact 16.09 km, an error of well under 1 percent. For 50 miles the shortcut gives 80 km against the exact 80.47 km, still good enough for planning stops on a drive.
Third, the 5 and 8 rule: 5 miles is about 8 kilometers, exactly 8.05 km, and 8 kilometers is about 5 miles, exactly 4.97 miles. This pair scales well because it is built from the real factor: 50 miles is about 80 km, and 500 miles is about 800 km. It is a memory aid, not a method, and its results should always be labeled as approximations.
Common Mistakes
Using the wrong factor is the most serious error. Multiplying kilometers by 1.609344 instead of 0.621371 inflates the answer by a factor of about 2.59, turning a 10 km run into a claimed 16.09 miles. The sanity check catches it instantly: the kilometer figure must always be the larger of the two numbers for the same distance.
Rounding the factor and then quoting a precise answer is a quieter error. A factor rounded to 0.62 supports an answer good to about two significant figures, not one quoted to four decimal places. Match the precision of the answer to the precision of the factor used to produce it, and when an answer matters, redo it with the full factor.
Converting a rounded label instead of the real figure causes the marathon trap described above. Converting 26.2 miles gives 42.16 km, not the official 42.195 km, because 26.2 was already rounded down from 26.22. Always convert the original, unrounded figure when one is available.
Treating every mile as the same mile is another trap. The statute mile of 1,609.344 meters is the standard for roads in the United States and the United Kingdom. The nautical mile of 1,852 meters belongs to sea and air navigation. Converting a nautical distance with the road factor understates it by about 15 percent.
Finally, converting the distance but forgetting the speed, or the reverse. A dashboard, a sign, and a training app may each use a different unit, and each figure needs its own conversion. The arithmetic is identical and quick, but it has to actually be done, figure by figure.
Frequently Asked Questions
How many kilometers are in 1 mile?
Exactly 1.609344 kilometers, usually rounded to 1.61 km. The figure is exact because the mile is defined as 5,280 feet and the foot is defined as exactly 0.3048 meters, so 5,280 x 0.3048 gives exactly 1,609.344 meters.
How many miles are in 1 kilometer?
0.621371 miles, usually rounded to 0.62 miles. To convert any kilometer distance to miles, multiply it by 0.621371: 5 km is 3.11 miles, and 10 km is 6.21 miles.
How many miles is 100 kilometers?
62.14 miles. The calculation is 100 x 0.621371 = 62.1371, rounded to 62.14. In the other direction, 100 miles is 160.93 kilometers, which shows why the unit must always be stated with the number.
How long is a 5K in miles?
A 5K is 5 kilometers, which is 3.11 miles. A 10K is 10 kilometers, which is 6.21 miles. A half marathon is 21.0975 km, or 13.11 miles, and a full marathon is 42.195 km, or 26.22 miles, usually quoted as 26.2 miles.
Is a kilometer longer than a mile?
No. A mile is longer than a kilometer. One mile is 1.609344 kilometers, so a kilometer is only about 62 percent of a mile. For any given distance, the kilometer count is always the larger number and the mile count always the smaller.
How do I convert kilometers per hour to miles per hour?
Multiply by 0.621371, the same factor used for distance, because the hour is the same on both sides of the conversion. So 50 km/h is 31.07 mph, 100 km/h is 62.14 mph, and 130 km/h is 80.78 mph. To go the other way, multiply miles per hour by 1.609344: 70 mph is 112.65 km/h.
What is the fastest way to estimate the conversion in my head?
Use the approximations, and label them as approximations. Multiply kilometers by 0.6 and add a little for miles, multiply miles by 1.6 for kilometers, or use the 5 and 8 rule: 5 miles is about 8 km, and 8 km is about 5 miles. For anything with a legal or safety consequence, use the full factors instead.
Why does my pace look worse in miles than in kilometers?
Because a mile is longer than a kilometer, the same speed takes more minutes to cover a mile. A pace of 5:00 per kilometer is about 8:03 per mile. The speed has not changed; only the length of the unit it is measured against has changed. Pace conversions use the factors in the opposite direction from distance conversions for this reason.
Is a nautical mile the same as a regular mile?
No. The regular statute mile is exactly 1,609.344 meters. The nautical mile used in sea and air navigation is exactly 1,852 meters, or 1.852 km, about 15 percent longer. Check which mile a distance uses before converting it.
How do I check a conversion without redoing the whole calculation?
Apply the sanity check: for the same distance, the kilometer number must be larger than the mile number. Then, if the figure matters, convert it back with the opposite factor. A correct conversion returns to the starting figure, apart from rounding. A conversion done with the wrong factor fails both checks at once.
Keep reading: Meters in a Foot
Sources & references
- National Institute of Standards and Technology, NIST Guide to the SI, Appendix B: Conversion Factors (Special Publication 811). Used for the 1959 change of definition under which the yard is exactly 0.9144 meters and the foot is exactly 0.3048 meters, and for the international mile as 5,280 international feet, from which 1 mile = 1,609.344 meters exactly. https://www.nist.gov/pml/special-publication-811/nist-guide-si-appendix-b-conversion-factors
- National Institute of Standards and Technology, Handbook 44, Appendix C: General Tables of Units of Measurement. Used for 8 furlongs = 1 mile = 5,280 feet, and for 1,852 meters = 1 international nautical mile. https://www.nist.gov/system/files/documents/2024/01/14/NIST%20HB%2044%202024%20Appendix%20C%20General%20Tables%20of%20Units%20of%20Measurement.pdf
- World Athletics, The Measurement of Road Race Courses (World Athletics in co-operation with AIMS, revised edition 2023). Used for the standard road race distances recognised for records, including the half marathon at 21.0975 km and the marathon at 42.195 km. https://media.aws.iaaf.org/competitioninfo/2023 Course Measurement Book - ENG.pdf
