How to Convert Miles to Kilometers

The one number to remember

One international mile is exactly 1.609344 kilometers. That figure is not a measurement that was rounded later; it is a definition. In 1959 the United States, the United Kingdom and four other countries agreed to define the international yard as exactly 0.9144 meters. A mile is 1,760 yards, so 1,760 × 0.9144 gives 1,609.344 meters, or 1.609344 kilometers.

Because the factor is exact, any rounding in your answer comes from you rather than from the conversion. In the other direction, one kilometer is 1 ÷ 1.609344 miles, which is about 0.621371. That decimal does not terminate, so it is always rounded, and 0.6214 is plenty for everyday use.

This is also why the mile feels awkward to convert by hand: 1.609344 has six decimal places, and no simple fraction reproduces it exactly. Rounded factors such as 1.6 or 1.61 are fine for estimates, but keep all six decimals whenever the result will be reused in further calculations.

Miles to kilometers, step by step

To convert miles to kilometers, multiply the number of miles by 1.609344. It helps to write the units into the calculation: 10 mi × 1.609344 km/mi = 16.09344 km. The miles cancel and kilometers remain, which is a good sign that you multiplied rather than divided.

Here is a longer example. For 26.2 miles, 26 × 1.609344 = 41.842944 and 0.2 × 1.609344 = 0.3218688, so the total is 42.1648128 km, or about 42.16 km. The official marathon distance is 42.195 km, a length taken from the 1908 London Olympic course of 26 miles and 385 yards, and 26.2 miles is only a rounded version of that.

Decide how many digits you need before you start. A trip of 120 miles is about 193 km, and nobody planning a drive needs the digits after that.

Kilometers to miles

To go the other way, divide kilometers by 1.609344, or multiply by 0.621371. For 100 km, 100 ÷ 1.609344 = 62.137 miles, rounded to three decimals. For 5 km the answer is 3.10686 miles, and for 10 km it is 6.21371 miles.

Suppose a road sign shows 35 km to the next town. Multiplying 35 × 0.621371 gives 21.748 miles, so about 21.7 miles. Dividing 35 by 1.609344 gives the same answer, because multiplying by 0.621371 and dividing by 1.609344 are the same operation.

A quick direction check catches most mistakes. A mile is longer than a kilometer, so a distance always has a smaller number in miles than in kilometers. If your kilometer-to-mile result came out larger than the input, you multiplied by the wrong factor.

• 1 mi = 1.609344 km
• 5 mi = 8.04672 km
• 10 mi = 16.09344 km
• 1 km ≈ 0.621371 mi
• 5 km ≈ 3.10686 mi
• 10 km ≈ 6.21371 mi

Mental shortcuts that work

The simplest estimate is to multiply miles by 1.6. It runs about 0.6 percent low, because 1.6 is slightly below the true factor. For 50 miles it gives 80 km against an exact 80.4672 km, a gap of under half a kilometer.

A neater trick uses the Fibonacci sequence: 5, 8, 13, 21, 34. Consecutive terms have a ratio close to 1.6, so 5 miles is about 8 km, 8 miles about 13 km, and 13 miles about 21 km. The exact value for 13 miles is 20.92 km. For other numbers, split them into pieces that you can look up, such as 20 miles as 13 plus 5 plus 2.

For kilometers to miles, multiply by 0.62. A 100 km distance becomes 62 miles, which is within a fraction of a percent of the exact 62.14.

Speeds and other miles that are not the same

Speed uses the same factor, because miles per hour is simply miles divided by hours and the hour cancels. A limit of 60 mph is 96.56064 km/h, and 70 mph is 112.65408 km/h. In reverse, 100 km/h is about 62.14 mph.

Not every mile is the international mile. A nautical mile is a different unit, defined as exactly 1,852 meters, or 1.852 km, and it is used at sea and in the air. The old US survey mile was based on the US survey foot and differs from the international mile by about 3 millimeters; the survey foot was deprecated at the end of 2022. For everyday travel, the statute mile of 1.609344 km is the one people mean.

Checking the result

Two quick checks are worth the few seconds. First, confirm the direction: miles to kilometers should grow by roughly 60 percent, and kilometers to miles should shrink by about 38 percent. Second, compare with a shortcut such as multiplying by 1.6; if the exact answer and the estimate are far apart, something was mistyped.

A unit converter such as this one has mile and kilometer in its Length category, shows the equation, and lets you choose the number of decimal places, so you can match the precision to the job. It also accepts a comma as the decimal separator. For navigation, surveying, legal or engineering work, always check the original source for the required unit and precision.