Mach Number Calculator
Convert between true airspeed and Mach number in either direction. The speed of sound depends on air temperature, which you can enter directly or derive from a pressure altitude under the standard atmosphere.
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Understanding Mach Number
The speed of sound in air depends on temperature, not pressure. At standard sea-level conditions (15°C / 59°F), the speed of sound is approximately 661 knots. At FL350 with standard temperature (−54°C / −65°F), it is approximately 576 knots.
Most light GA aircraft never approach Mach numbers where compressibility effects are significant. This calculator is most relevant for high-performance piston aircraft, turboprops, and jets.
Critical Mach (Mcrit) is the airspeed at which airflow over the wing first reaches the speed of sound locally, even though the aircraft’s overall speed is subsonic. Exceeding Mcrit can cause buffet, loss of control effectiveness, and Mach tuck. Mcrit is specified in the aircraft’s POH or AFM for aircraft where it is relevant.
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Frequently Asked Questions
This calculator is for educational and planning purposes only. Always refer to your aircraft's POH/AFM, current NOTAMs, and official weather briefings. No calculator is a substitute for pilot-in-command judgment or CFI guidance.
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