Physics

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Mach Number Calculator.

Calculate Mach number from speed and local speed of sound.

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Mach number: 0.991254

Mach number

0.000000

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Use Cases

Aerospace Engineering

Determine whether an aircraft or projectile is subsonic, transonic, or supersonic by calculating its Mach number from speed and local sound speed.

Example: An aircraft flying at 300 m/s in air where sound speed is 340 m/s has Mach 0.88.

Physics Education

Help students understand the concept of Mach number and its dependence on the speed of sound in different media.

Example: Calculate Mach number for a bullet at 800 m/s in air (sound speed 343 m/s) to see it's Mach 2.33.

Frequently Asked Questions

What is Mach number?
Mach number is the ratio of an object's speed to the speed of sound in the surrounding medium. It indicates how fast an object moves relative to sound, with values below 1 subsonic, equal to 1 sonic, and above 1 supersonic.
How do I use this calculator?
Enter the object's speed in meters per second (m/s) and the local speed of sound in m/s. The calculator divides the object speed by the speed of sound to give the Mach number. Ensure both values are positive and in the same units.
What is the local speed of sound?
The local speed of sound is the speed at which sound waves travel in a specific medium (like air) under given conditions (temperature, pressure, altitude). It varies with these conditions; for example, at sea level and 20°C, it's about 343 m/s.

Tips & Common Mistakes

Tips

  • Ensure both speed values are in meters per second (m/s) for accurate results.
  • The local speed of sound varies with temperature and altitude; use the correct value for your conditions.
  • A Mach number less than 1 means subsonic, equal to 1 is sonic, and greater than 1 is supersonic.
  • For high-speed flows, consider that the speed of sound changes with temperature, so use local values.

Common Mistakes to Avoid

  • Using different units for speed and sound speed without converting, leading to incorrect Mach numbers.
  • Entering a negative speed or sound speed, which is physically meaningless.
  • Assuming the speed of sound is constant at 343 m/s regardless of altitude or temperature.

Last updated: August 13, 2026