Waves
Mach Number
Ratio of object speed to speed of sound. M > 1 is supersonic.
Variables
Munitless
Mach number
Dimensionless velocity ratio
Allowed values: greater than 0
vm/s
Object velocity
Speed of moving object
vsoundm/s
Speed of sound
In the medium
Allowed values: greater than 0
Derivation
By definition. M < 1 subsonic, M = 1 sonic, M > 1 supersonic, M > 5 hypersonic.
Your notes
0/5000
Check value
Round inputs run through this page's calculator. Use it to test your own working or a rearranged form. It is a test case, not a real-world example.
- v = 2 m/s (Object velocity)
- vsound = 3 m/s (Speed of sound)
Result: M = 0.66666667
Where this formula is listed
- Waves formulas, under Sound Waves, alongside Sound Level (Decibels), Beat Frequency and Sound Intensity Level Addition.
- In the waves list it comes after Beat Frequency and before Shock Wave Angle (Mach Cone).
- Waves formula sheet, one of 37 formulas printed with symbol keys and SI units.
- The full formula index, grouped by category and topic.
Common questions
What is the Mach Number formula?
Mach Number is written M = v/v_sound. Ratio of object speed to speed of sound. M > 1 is supersonic. It belongs to Waves, under Sound Waves.
What are the units in M = v/v_sound?
In SI units, M is mach number (dimensionless); v is object velocity, measured in m/s; v_s ound is speed of sound, measured in m/s.
How is the Mach Number formula derived?
By definition. M < 1 subsonic, M = 1 sonic, M > 1 supersonic, M > 5 hypersonic. The result is M = v/v_sound.