Convert Feet per Second to Miles per Hour
Feet per second to miles per hour is the conversion that connects the way physics problems and radar guns describe speed with the number on a car's speedometer. One foot per second works out to about 0.681818 miles per hour, so the number gets noticeably smaller when you switch from ft/s to mph.
Feet per second to Miles per hour conversion table
| Feet per second (ft/s) | Miles per hour (mph) |
|---|---|
| 1 | 0.681818 |
| 2 | 1.363636 |
| 3 | 2.045455 |
| 5 | 3.409091 |
| 10 | 6.818182 |
| 20 | 13.636364 |
| 50 | 34.090909 |
| 100 | 68.181818 |
| 500 | 340.909091 |
| 1,000 | 681.818182 |
The formula
To convert feet per second to miles per hour, multiply the speed in feet per second by 0.681818:
miles per hour = feet per second × 0.681818
A worked example
The cleanest example is the classic driving identity — a car moving at 88 feet per second:
88 × 0.681818 = 60.0 mph
That's exactly highway speed, and it's the reason 88 ft/s shows up so often in physics and driver's-ed textbooks: it's the exact feet-per-second equivalent of 60 mph.
Why it's an approximation
Feet per second and miles per hour don't line up on a clean decimal — the exact ratio is 15/22, which as a decimal repeats forever (0.6818181818...). The relationship between the units is precise (88 ft/s always equals exactly 60 mph), but writing that ratio as "0.681818" is a rounded stand-in for a number that never actually terminates.
When you'll use it
Turning a radar-gun or physics-problem speed given in feet per second into the miles-per-hour figure you'd see on a speedometer, checking projectile or pitch speeds against everyday driving speeds, and working through classic "88 ft/s = 60 mph" style problems.
Frequently asked questions
How many miles per hour are in a foot per second?
About 0.681818 mph. It's a repeating decimal (15/22 as a fraction), so any figure you see displayed is rounded slightly, even though the underlying relationship between the two units is fixed.
Is the feet-per-second to miles-per-hour conversion exact?
The relationship itself is exact — 88 feet per second is exactly 60 miles per hour, no rounding at all — but the per-unit factor, 0.681818, is a repeating decimal, so any decimal version of it is an approximation of that exact ratio.
What's a quick way to estimate feet per second in miles per hour?
Divide by 1.47, or just remember that 88 ft/s is exactly 60 mph. For a rough mental check, 44 ft/s (half of 88) is 30 mph.