MPH to FPS: Mental Calculation of Miles per Hour to Feet per Second

How to Instantly Convert MPH to FPS When Driving

- The Quick and Easy Math Trick -

Simply divide miles-per-hour by 2, then multiply the result by 3 to find feet-per-second.

This is the easy, quick math way and gives a fairly accurate answer. Your answer will be accurate within 5%. As an example, 100 mph converts to 150 fps. If one does the more complicated method of math calculation (detailed further down the page), the resulting answer would be 147 fps.

"How many feet per second..." is a math question usually relating to cars and driving.

Easy Table Conversion from MPH to FPS Examples Chart

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


The More Difficult (and More Accurate) Answer

To prove the quick math shortcut calculation works:
  1. First. convert MPH (miles-per-hour) to MPM (miles-per-minute) by dividing MPH by 60.
  2. Then convert miles to feet. There are 5,280 feet in one mile, so multiply MPM by 5,280 to get FPM (feet-per-minute).
  3. Lastly, convert FPM to FPS (feet-per-second) 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?
  1. Conversion from mph to fps is as follows: If we divide by 60, we get miles-per-minute: 25/60 = .416667.
  2. 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].
  3. To convert from feet-per-minute to feet-per-second, we divide the answer by 60: 2199.99/60 = ~36.667 feet-per second.
  4. 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?
  1. 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.
  2. 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.
  3. To convert from feet-per-minute to feet-per-second, we divide the answer by 60: 5725.28/60 = ~95.421 feet-per second, which is the answer.
  4. 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.
  1. If we divide by 60, we get miles-per-minute: 120/60 = 2.000. This again makes sense. After all, 60 miles an hour is a the usual mile-a-minute. So 120 mph would be 2-miles-a-minute.
  2. 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.
  3. To convert from feet-per-minute to feet-per-second, we divide the answer by 60: 10560/60 = ~176 feet-per second.
  4. This number is within 5% of the table above which says 120 mph equals 180 fps.

FPS to MPH

Quick way to find reverse, i.e., convert from feet-per-second to miles-per hour: divide fps by 3 and then multiply by 2 for mph.

Easy Table Conversion from FPS to MPH Examples Chart

FPS
MPH
10
6.67
20
13.33
25
16.67
40
26.68
50
33.33
75
50
100
66.67
150
100
200
133.33
500
333.33
1000
666.67

Doing 20 Miles-per-Hour? That Is 30 Feet-per-Second.

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