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 mach (approx at sea level)?

Mach is a dimensionless speed unit expressing the ratio of an object’s speed to the local speed of sound. At sea level, Mach 1 is approximately 343 m/s. It is used in aviation and aerodynamics to characterise high-speed flight regimes.

Real-world uses

Mach numbers are used in aerospace engineering and aviation to describe aircraft speed relative to the speed of sound. Commercial jets cruise near Mach 0.85, military fighters reach Mach 2+, and hypersonic vehicles exceed Mach 5.

History

Named after Austrian physicist Ernst Mach, who studied supersonic projectiles in the 1880s. The Mach number was formally defined by Swiss engineer Jakob Ackeret in 1929. Chuck Yeager first broke the sound barrier (Mach 1) in 1947 in the Bell X-1.

Common mistakes

Treating Mach as a fixed speed—it varies with altitude and temperature because the speed of sound changes. Mach 1 is about 343 m/s at sea level (15°C) but about 295 m/s at 11,000 m altitude.

When is this conversion used?

Converting foot per second to mach (approx at sea level) 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 = 0.00089571 mach (approx at sea level)

1 mach (approx at sea level) = 340.29 metre per second

How to convert foot per second to mach (approx at sea level)

To convert foot per second to mach (approx at sea level), multiply the value by 0.00089571.

To convert mach (approx at sea level) back to foot per second, multiply by 1,116.43700787.

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 mach (approx at sea level)

foot per second	mach (approx at sea level)
0.1	0.00008957
0.5	0.00044785
1	0.00089571
2	0.00179141
5	0.00447853
10	0.00895707
25	0.02239267
50	0.04478533
100	0.08957066
250	0.22392665
500	0.4478533
1,000	0.8957066

Common values

	foot per second	mach (approx at sea level)
Walking speed	4.59317585 foot per second	0.00411414 mach (approx at sea level)
City speed limit	45.60367454 foot per second	0.04084751 mach (approx at sea level)
Highway driving	102.69028871 foot per second	0.09198037 mach (approx at sea level)
Commercial aircraft	820.20997375 foot per second	0.73466749 mach (approx at sea level)
Speed of sound (sea level)	1,116.43700787 foot per second	1 mach (approx at sea level)

Available Speed units

More foot per second conversions

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