Mach (Ma)

ScientificCurrent unitApproximate value

The speed of sound at sea level in standard conditions (15 °C): about 340.294 m/s or 1,225 km/h. The speed of sound varies with temperature and altitude.

1 Mach = 340.294 meters per second (approximately).

Approximate value. Standards for the Mach varied by place and period, so this converter uses the most commonly cited value. Treat results as estimates, not exact figures.

About the Mach

Ernst Mach, the Austrian physicist and philosopher born in Moravia in 1838, never defined a unit of speed, yet the ratio carries his name. In 1887 he and Peter Salcher presented a paper on photographing processes in air caused by projectiles, including a shadowgraph of the bow shock around a supersonic bullet fired from a Werndl carbine. The ratio of flow speed to the local speed of sound was later named for him.

Mach is therefore a dimensionless number, not a fixed speed, and because the speed of sound depends on temperature, so does Mach 1. It is about 340 m/s (1,225 km/h) in dry air at 15 °C at sea level, 343 m/s at 20 °C, and about 295 m/s above 11 kilometers where the air is cold. Flight is called subsonic below 0.8, transonic from 0.8 to 1.2, supersonic from 1.2 to 5 and hypersonic from 5 to 10. On 14 October 1947 Chuck Yeager flew the Bell X-1 to Mach 1.06, reported as 361 m/s.

Sources: Wikipedia: Mach number; Wikipedia: Ernst Mach; Wikipedia: Speed of sound

Mach conversion chart

1 Mach expressed in every other speed unit:

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