The Mach number () is a dimensionless quantity used in fluid dynamics to represent the ratio of the speed of an object to the speed of sound in the surrounding medium. In subsonic flow (where M<1), the velocity of the object is lower than the speed of sound, while in supersonic flow (where M>1), the velocity exceeds the speed of sound. The formula to calculate Mach number (M) as follows:
where:
- Â is the Mach number,
- is the velocity of the object (in meters per second),
- is the speed of sound in the surrounding medium (in meters per second).