Conversion formula

The conversion factor from miles to kilometers is 1.609344, which means that 1 mile is equal to 1.609344 kilometers:

1 mi = 1.609344 km

To convert 421.4 miles into kilometers we have to multiply 421.4 by the conversion factor in order to get the length amount from miles to kilometers. We can also form a simple proportion to calculate the result:

1 mi → 1.609344 km

421.4 mi → L_(km)

Solve the above proportion to obtain the length L in kilometers:

L_(km) = 421.4 mi × 1.609344 km

L_(km) = 678.1775616 km

The final result is:

421.4 mi → 678.1775616 km

We conclude that 421.4 miles is equivalent to 678.1775616 kilometers:

421.4 miles = 678.1775616 kilometers

Alternative conversion

We can also convert by utilizing the inverse value of the conversion factor. In this case 1 kilometer is equal to 0.0014745400859927 × 421.4 miles.

Another way is saying that 421.4 miles is equal to 1 ÷ 0.0014745400859927 kilometers.

Approximate result

For practical purposes we can round our final result to an approximate numerical value. We can say that four hundred twenty-one point four miles is approximately six hundred seventy-eight point one seven eight kilometers:

421.4 mi ≅ 678.178 km

An alternative is also that one kilometer is approximately zero point zero zero one times four hundred twenty-one point four miles.

Conversion table

miles to kilometers chart

For quick reference purposes, below is the conversion table you can use to convert from miles to kilometers