Mach number (Mach) - Unit Information & Conversion
What is a Mach number?
Definition
The Mach number (M or Ma) is a dimensionless quantity in fluid dynamics representing the ratio of flow velocity past a boundary to the local speed of sound. It is named after Austrian physicist and philosopher Ernst Mach.
History
The term "Mach number" was proposed by Swiss aeronautical engineer Jakob Ackeret in 1929. It gained prominence during World War II with the development of high-speed aircraft. The sound barrier (Mach 1) was famously broken by Chuck Yeager in 1947.
Common Uses
- Aerospace: Describing the speed of aircraft and spacecraft relative to the speed of sound (subsonic, transonic, supersonic, hypersonic).
- Fluid Dynamics: Analyzing high-speed flows in wind tunnels, jet engines, and rocket nozzles.
- Ballistics: Characterizing the speed of projectiles.
Unit FAQs
What does Mach 1 mean?
Mach 1 represents the speed of sound in the surrounding medium under specific conditions (temperature, pressure, altitude). At standard sea level conditions (15°C and 1 atm), Mach 1 is approximately 343 meters per second (1,235 km/h; 767 mph).
Is the speed of Mach 1 constant?
No, the speed of sound varies primarily with temperature. It decreases at higher altitudes where the air is colder. Therefore, the actual speed corresponding to Mach 1 changes with altitude and atmospheric conditions.
What are the different speed regimes related to Mach number?
- Subsonic: M < 0.8
- Transonic: 0.8 ≤ M < 1.2
- Supersonic: 1.2 ≤ M < 5
- Hypersonic: M ≥ 5
Mach number Conversion Formulas
To Meter per second:
To Kilometer per hour:
To Mile per hour:
To Foot per second:
To Knot:
To Speed of light:
Convert Mach number
Need to convert Mach number to other speed units? Use our conversion tool.