## Conversion formula

The conversion factor from feet per second to miles per hour is 0.68181818181818, which means that 1 foot per second is equal to 0.68181818181818 miles per hour:

1 ft/s = 0.68181818181818 mph

To convert 399 feet per second into miles per hour we have to multiply 399 by the conversion factor in order to get the velocity amount from feet per second to miles per hour. We can also form a simple proportion to calculate the result:

1 ft/s → 0.68181818181818 mph

399 ft/s → V(mph)

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

V(mph) = 399 ft/s × 0.68181818181818 mph

V(mph) = 272.04545454545 mph

The final result is:

399 ft/s → 272.04545454545 mph

We conclude that 399 feet per second is equivalent to 272.04545454545 miles per hour:

399 feet per second = 272.04545454545 miles per hour

## Alternative conversion

We can also convert by utilizing the inverse value of the conversion factor. In this case 1 mile per hour is equal to 0.0036758563074353 × 399 feet per second.

Another way is saying that 399 feet per second is equal to 1 ÷ 0.0036758563074353 miles per hour.

## Approximate result

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

399 ft/s ≅ 272.045 mph

An alternative is also that one mile per hour is approximately zero point zero zero four times three hundred ninety-nine feet per second.

## Conversion table

### feet per second to miles per hour chart

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

feet per second (ft/s) miles per hour (mph)
400 feet per second 272.727 miles per hour
401 feet per second 273.409 miles per hour
402 feet per second 274.091 miles per hour
403 feet per second 274.773 miles per hour
404 feet per second 275.455 miles per hour
405 feet per second 276.136 miles per hour
406 feet per second 276.818 miles per hour
407 feet per second 277.5 miles per hour
408 feet per second 278.182 miles per hour
409 feet per second 278.864 miles per hour