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 knot?

A knot is a unit of speed equal to one nautical mile per hour, approximately 1.852 km/h. It is the international standard for maritime navigation, aviation, and meteorological wind speed reporting.

Real-world uses

Knots are the universal speed unit in maritime navigation and aviation worldwide, regardless of whether a country uses metric or imperial. Ship speeds, ocean currents, wind speed in aviation weather (METAR) reports, and jet stream velocities are all given in knots.

History

The knot originates from the 17th-century practice of measuring ship speed by throwing a log overboard attached to a rope with knots tied at regular intervals. Sailors counted how many knots paid out in a fixed time (measured by a sandglass).

Common mistakes

Saying "knots per hour"—a knot already means nautical miles per hour, so adding "per hour" is redundant and incorrect. Also, confusing knots with km/h: 1 knot ≈ 1.852 km/h.

When is this conversion used?

Converting foot per second to knot is useful in the speed domain when comparing values across different measurement standards or applying formulas that require a specific unit.

Worked examples

1 foot per second = 0.5924838 knot

1 knot = 0.51444444 metre per second

How to convert foot per second to knot

To convert foot per second to knot, multiply the value by 0.5924838.

To convert knot back to foot per second, multiply by 1.68780986.

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 knot

foot per second	knot
0.1	0.05924838
0.5	0.2962419
1	0.5924838
2	1.1849676
5	2.96241901
10	5.92483801
25	14.81209503
50	29.62419007
100	59.24838013
250	148.12095034
500	296.24190067
1,000	592.48380135

Common values

	foot per second	knot
Walking speed	4.59317585 foot per second	2.72138229 knot
City speed limit	45.60367454 foot per second	27.01943845 knot
Highway driving	102.69028871 foot per second	60.84233262 knot
Commercial aircraft	820.20997375 foot per second	485.96112315 knot
Speed of sound (sea level)	1,116.43700787 foot per second	661.47084239 knot

Available Speed units

More foot per second conversions

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