Conversion formula

The conversion factor from miles per hour to kilometers per hour is 1.6093439999987, which means that 1 mile per hour is equal to 1.6093439999987 kilometers per hour:

1 mph = 1.6093439999987 km/h

To convert 421 miles per hour into kilometers per hour we have to multiply 421 by the conversion factor in order to get the velocity amount from miles per hour to kilometers per hour. We can also form a simple proportion to calculate the result:

1 mph → 1.6093439999987 km/h

421 mph → V_(km/h)

Solve the above proportion to obtain the velocity V in kilometers per hour:

V_(km/h) = 421 mph × 1.6093439999987 km/h

V_(km/h) = 677.53382399946 km/h

The final result is:

421 mph → 677.53382399946 km/h

We conclude that 421 miles per hour is equivalent to 677.53382399946 kilometers per hour:

421 miles per hour = 677.53382399946 kilometers per hour

Alternative conversion

We can also convert by utilizing the inverse value of the conversion factor. In this case 1 kilometer per hour is equal to 0.0014759410741991 × 421 miles per hour.

Another way is saying that 421 miles per hour is equal to 1 ÷ 0.0014759410741991 kilometers per hour.

Approximate result

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

421 mph ≅ 677.534 km/h

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

Conversion table

miles per hour to kilometers per hour chart

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