Mach (20°C, 1 atm) to Foot per Hour

Mach number is the ratio of an object's speed to the speed of sound in the surrounding medium. Mach 1 at 20°C, 1 atm equals approximately 343.6 m/s (1,235 km/h).

Mach = velocity ÷ speed_of_sound. At 20°C: Mach 1 = 343.6 m/s. Speed of sound = √(γRT/M) where γ = heat capacity ratio.

To m/s (at 20°C): × 343.6. To km/h (at 20°C): × 1,237. Note: changes with altitude and temperature.

Fighter jets (Mach 1.5–2.5), commercial aircraft (Mach 0.8–0.85), space shuttle reentry (Mach 25), and missile speeds.

Concorde: Mach 2.04. SR-71 Blackbird: Mach 3.3. X-15: Mach 6.7. Meteorites enter at Mach 50+. Subsonic <1, supersonic >1, hypersonic >5.

Thinking Mach is constant — it varies with temperature/altitude. At 30,000 ft, Mach 1 ≈ 295 m/s (colder air = slower sound).

Mach 1 = speed of sound. Below Mach 1 = subsonic. Mach 1–5 = supersonic. Above Mach 5 = hypersonic. It's a ratio, not a fixed speed.

Foot per hour measures distance in feet traveled over one hour. Used for very slow movements in imperial units.

1 ft/h = 0.000085 m/s = 0.0003048 km/h = 0.3048 m/h.

To ft/s: ÷ 3,600. To mph: ÷ 5,280. To m/s: × 0.000085.

Glacier movement in US studies, very slow industrial processes, and some geological measurements.

Some glaciers move at 50–500 ft/h. Very slow conveyor systems might use this unit.

Confusing with ft/min (60× faster) or ft/s (3,600× faster).

5,280 ft/h = 1 mph. Extremely slow. Rarely used outside specialized contexts.