Mach and True Airspeed Calculator
Convert a Mach number into true airspeed using the outside static air temperature. For example, Mach 0.78 at -56.5 °C gives about 447 knots.
Formula
Speed of sound a = 38.9679 × √T knots, where T is the static air temperature in kelvin (°C + 273.15). True airspeed = Mach number × a. Use static air temperature (SAT), not total air temperature (TAT), which is higher because of ram rise.
FAQ
What is the speed of sound at cruise altitude?
In standard conditions at 36,000 ft the temperature is about -56.5 °C and the speed of sound is about 573 knots, so Mach 0.78 is a true airspeed of about 447 knots.
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