Conversion formula

The conversion factor from miles per hour to feet per second is 1.4666666666667, which means that 1 mile per hour is equal to 1.4666666666667 feet per second:

1 mph = 1.4666666666667 ft/s

To convert 639.9 miles per hour into feet per second we have to multiply 639.9 by the conversion factor in order to get the velocity amount from miles per hour to feet per second. We can also form a simple proportion to calculate the result:

1 mph → 1.4666666666667 ft/s

639.9 mph → V_(ft/s)

Solve the above proportion to obtain the velocity V in feet per second:

V_(ft/s) = 639.9 mph × 1.4666666666667 ft/s

V_(ft/s) = 938.52 ft/s

The final result is:

639.9 mph → 938.52 ft/s

We conclude that 639.9 miles per hour is equivalent to 938.52 feet per second:

639.9 miles per hour = 938.52 feet per second

Alternative conversion

We can also convert by utilizing the inverse value of the conversion factor. In this case 1 foot per second is equal to 0.0010655073946213 × 639.9 miles per hour.

Another way is saying that 639.9 miles per hour is equal to 1 ÷ 0.0010655073946213 feet per second.

Approximate result

For practical purposes we can round our final result to an approximate numerical value. We can say that six hundred thirty-nine point nine miles per hour is approximately nine hundred thirty-eight point five two feet per second:

639.9 mph ≅ 938.52 ft/s

An alternative is also that one foot per second is approximately zero point zero zero one times six hundred thirty-nine point nine miles per hour.

Conversion table

miles per hour to feet per second chart

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