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MPH to FPS: Mentally Converting Miles Per Hour to Feet Per Second

Updated on January 05, 2017
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The Quick and Easy Answer

Divide MPH by 2, then multiply by 3 to find FPS.

Converting MPH to FPS? The How-to, Quick and Easy Method.

Divide Miles-per-Hour by 2, then multiply by 3 to find Feet-per-Second.

This is the easy, quick math way, but it gives a fairly accurate answer. Your answer will be accurate to within 5%. As an example, 100 MPH converts to 150 FPS. If you did the more complicated math calculation (see below), you would get 147 FPS.

"How many feet per second..." is a math question usually related to cars and driving. The laws of physics seldom take a vacation....
"How many feet per second..." is a math question usually related to cars and driving. The laws of physics seldom take a vacation.... | Source

Easy Conversion from MPH to FPS

MPH
FPS
10
15
15
22.5
20
30
25
37.5
30
45
35
52.5
40
60
45
67.5
50
75
55
82.5
60
90
65
97.5
70
105
80
120
90
135
100
150
120
180
140
210
160
240
These calculations were done with the easy math way and are accurate within 5%.

The Harder (and More Accurate) Answer

1. First, you must convert MPH to MPM (minute) by dividing MPH by 60.

2. Second, convert miles to feet. There are 5,280 feet in one mile, so multiply MPM by 5,280 to get FPM.

3. Convert FPM to FPS by dividing by 60.

Examples of the Longhand Math Converting Miles-Per-Hour (MPH) to Feet-Per-Second (FPS)

Math Example One

You're going 25 mph. How many feet is that per second?

Conversion from mph to fps is as follows: If we divide by 60, we get miles-per-minute:

25/60 = .416667

For accuracy's sake, now is a good time to convert miles to feet. There are 5,280 feet in a mile so we multiply mpm times 5,280 to get feet-per-minute:

.416667 x 5280 = ~2199.99 feet-per-minute [note: "~" means approximate]

To convert from feet-per-minute to feet-per-second, we divide the answer by 60:

2199.99/60 = ~36.667 feet-per second.

This answer is within 5% of the one you get doing the easy math, which says 25 mph equals 37.5 fps.

Math Example Two

65 mph. How many feet per second?

Conversion from mph to fps is as follows: If we divide by 60, we get miles-per-minute.

65/60 = 1.0843333333333

This makes sense. After all, 60 miles an hour is obviously equal to a mile-a-minute.

For accuracy's sake, now is a good time to convert miles to feet. There are 5,280 feet in a mile, so we multiply the miles-per-minute times 5,280 to get feet-per-minute:

1.0843333333333 x 5280 = ~5725.28 feet-per-minute [note: "~" means approximate]

To convert from feet-per-minute to feet-per-second, we divide the answer by 60:

5725.28/60 = ~95.421 feet-per second.

This coincides within 5% of the table above, which says 65 mph equals 97.5 fps.

Math Example Three

120 mph is how many feet per second? Conversion from mph to fps is as follows. If we divide by 60, we get miles-per-minute:

120/60 = 2.000

This makes sense. After all, 60 miles an hour is obviously equal to a mile-a-minute. So 120 mph would be 2-miles-a-minute.

For accuracy's sake, now is a good time to convert miles to feet. There are 5,280 feet in a mile, so we multiply the miles-per-minute times 5,280 to get feet-per-minute:

2 x 5280 = ~10560 feet-per-minute [note: "~" means approximate]

To convert from feet-per-minute to feet-per-second, we divide the answer by 60:

10560/60 = ~176 feet-per second.

This number is within 5% of the table above which says 120 mph equals 180 fps.

FPS to MPH

Quick way to find the reverse, i.e. convert from fps to mph:

Divide FPS by 3 and then multiply by 2 to get MPH

Some Examples:

10 fps = 6.67 mph

25 fps = 16.67 mph

50 fps = 33.33 mph

100 fps = 66.67 mph

150 fps = 100 mph

Again, the "within 5% accuracy" caveat applies.

Doing 20 Miles-Per-Hour? That's 30 Feet-Per-Second

Most of these cars would not be able to stop in time.
Most of these cars would not be able to stop in time. | Source

It is hoped this math trick and rule-of-thumb will serve you well, especially on those rain and ice slicked roads.

The Most Ridiculous Car Chase Ever

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    • Eiddwen profile image

      Eiddwen 4 years ago from Wales

      Aahhh very useful indeed and thank you for sharing.

      Here's to so many more for us both to share on here.

      Eddy.

    • SkipF 3 months ago

      MPH to KNOTS is: Take 10%, halve that and add the two, then subtract from MPH. So 60MPH is 6+3 subtracted from 60...51KTS.

      then backwards:

      A plane going 400KTs is going (40+20) 460MPH...

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