What is foot per second?

Foot per second is a unit of speed in imperial and US customary systems. It is used in ballistics, sports science, and engineering calculations that rely on US customary units.

Real-world uses

Feet per second is used in ballistics for bullet muzzle velocities (e.g., 2,800 fps for a rifle round), aerospace engineering for aircraft approach speeds, and fluid dynamics in American engineering contexts. Elevator speeds are sometimes specified in ft/s.

History

Feet per second has been used in English-language engineering since the 18th century, particularly in artillery and ballistics. It remains the standard velocity unit in American firearms and aerospace industries despite the broader shift toward metric units.

Common mistakes

Confusing feet per second with miles per hour. 1 ft/s ≈ 0.682 mph, so they are quite different. Also, using fps as an abbreviation for both "feet per second" and "frames per second" creates ambiguity in technical documents.

What is mile per hour?

Mile per hour is a unit of speed equal to one mile travelled in one hour. It is the standard unit for road speeds, vehicle performance ratings, and weather reports in the United States and United Kingdom.

Real-world uses

Miles per hour is the standard speed unit for road traffic in the United States, the United Kingdom, and a few other countries. Baseball pitching speed, hurricane wind categories (Saffir-Simpson scale), and NASCAR race speeds are quoted in mph.

History

Miles per hour became the standard speed expression in English-speaking countries with the advent of railways and later automobiles. The first US speed limit (8 mph in New York City, 1901) and British speed cameras use mph as the legal standard.

Common mistakes

Assuming mph-to-km/h conversion is a simple ×1.5—the actual factor is 1.609. Also, forgetting that UK and US speed limits both use mph, which can mislead visitors from metric countries into driving too fast or too slow.

When is this conversion used?

Speed limits, vehicle speedometers, and weather reports for wind speeds use different units depending on the country, making km/h to mph conversion one of the most practical speed conversions.

Worked examples

1 foot per second = 0.68181818 mile per hour

1 mile per hour = 0.44704 metre per second

How to convert foot per second to mile per hour

To convert foot per second to mile per hour, multiply the value by 0.68181818.

To convert mile per hour back to foot per second, multiply by 1.46666667.

Measurement standards

The SI unit of speed is metres per second (m/s), a derived unit requiring no independent definition. The knot is defined as exactly one nautical mile (1,852 metres) per hour and is sanctioned for maritime and aeronautical navigation by the International Civil Aviation Organization.

Did you know?

The fastest human-made object is the Parker Solar Probe, which reached 635,266 km/h (about 176 km/s) in 2024 during a close pass of the Sun — fast enough to travel from New York to Tokyo in under a minute.

Quick reference: foot per second to mile per hour

foot per second	mile per hour
0.1	0.06818182
0.5	0.34090909
1	0.68181818
2	1.36363636
5	3.40909091
10	6.81818182
25	17.04545455
50	34.09090909
100	68.18181818
250	170.45454545
500	340.90909091
1,000	681.81818182

Common values

	foot per second	mile per hour
Walking speed	4.59317585 foot per second	3.13171081 mile per hour
City speed limit	45.60367454 foot per second	31.09341446 mile per hour
Highway driving	102.69028871 foot per second	70.01610594 mile per hour
Commercial aircraft	820.20997375 foot per second	559.23407301 mile per hour
Speed of sound (sea level)	1,116.43700787 foot per second	761.20705082 mile per hour

Available Speed units

More foot per second conversions

Assumption: Mach uses an approximate sea-level reference (about 340.29 m/s).