Feet per Second to Miles per Hour Converter | ft/s to mph

What this converter does

Both feet per second and miles per hour are speeds in the same system, but they answer different questions: ft/s suits short, quick motion, while mph suits travel. This converter turns a ft/s figure into mph, so a speed measured over feet and seconds reads in the everyday units you know. Enter the ft/s value and read off the mph.

The conversion factor

One foot per second is 0.681818 miles per hour, so:

mph = ft/s × 0.681818

The number comes from the units themselves: there are 5,280 feet in a mile and 3,600 seconds in an hour, and 3,600 divided by 5,280 gives that 0.681818. The mph figure comes out smaller than the ft/s, since a mile is a great many feet.

The 88 feet per second trick

There is one pairing here worth keeping for life: 88 feet per second is exactly 60 miles per hour. That is one mile every minute, which is where it comes from, 60 miles in 60 minutes. It makes a handy yardstick. If something is moving at 44 ft/s, that is half of 88, so 30 mph. At 176 ft/s it is double, so 120 mph. Anchoring on 88 equals 60 lets you place a lot of ft/s speeds without any real arithmetic.

A worked example

Say a baseball leaves the pitcher's hand at about 130 feet per second and you want that in mph.

• 130 × 0.681818 = 88.6 mph

So 130 ft/s is about 88.6 mph, which is right in the range of a hard major-league fastball. Converting the ft/s figure puts the pitch on the mph scale every fan reads it by, where the difference between an 89 and a 95 means something.

Common ft/s speeds in mph

The standout row is 88 ft/s landing exactly on 60 mph. Around it, 50 ft/s is about 34 mph and 100 ft/s is just over 68 mph.

Where it comes up

It shows up wherever motion is timed over feet but understood in mph. Sports is a common one, since pitch speeds, batted balls, and sprint splits are sometimes captured in ft/s and then reported in mph for the audience. Physics problems set in feet produce ft/s answers that are easier to grasp once turned into mph. And anyone reading a technical figure in ft/s who simply wants to know how fast that is in road terms reaches for this. It is the bridge from a short-scale speed to the travel speed you picture.

Questions people ask

How do I convert ft/s to mph?

Multiply the speed in ft/s by 0.681818. As a shortcut, remember that 88 ft/s is exactly 60 mph, and scale from there.

Why is 88 ft/s equal to 60 mph?

Because 60 mph is one mile every minute, and one mile is 5,280 feet covered in 60 seconds, which is 88 feet each second.

Why is the mph number smaller than the ft/s?

A mile is 5,280 feet, so a speed that sounds large in feet per second becomes a smaller number once measured in miles per hour.

References

1. National Institute of Standards and Technology (NIST), Special Publication 811, Guide for the Use of the International System of Units (unit conversion factors). https://www.nist.gov/pml/special-publication-811