Speed of Sound & Mach Number Calculator
Calculate Mach number, speed of sound in air (m/s, km/h, kts), and flight speed regimes.
Last reviewed by the myCalculator Editorial Team
Input Parameters
Calculation Results
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Formula & How Speed of Sound & Mach Number Calculator Works
The speed of sound in air depends only on the absolute temperature: a = 20.05 × √T, with T in kelvin and a in m/s. At 15°C (288.15 K) it is 340.3 m/s, or 661 knots. At the −56.5°C common at high cruise levels (216.65 K) it falls to 295.1 m/s, about 574 knots. Mach number is true airspeed divided by that local speed: an aircraft with a TAS of 450 knots in −56.5°C air is flying at Mach 0.78. This is why a jet's Mach number at a given TAS is higher at altitude. Mach limits matter for aircraft design, so always use the aircraft flight manual for real operations.
- Enter Ambient Air Temperature (°C): Input your target parameter value.
- Enter True Airspeed (TAS - kts): Input your target parameter value.
- Apply Formula: Calculate using
Speed of Sound a = 20.05 × √(T_Kelvin) m/s | Mach = TAS / a. - Review Results: View exact computed answers, metrics, and worked mathematical proofs.
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MyCalculator.com.au. (2026). Speed of Sound & Mach Number Calculator. Retrieved October 24, 2026, from https://www.mycalculator.com.au/calculators/physics/speed-of-sound
MyCalculator.com.au. (2026) 'Speed of Sound & Mach Number Calculator'. Available at: https://www.mycalculator.com.au/calculators/physics/speed-of-sound (Accessed: 24 October 2026).
Frequently Asked Questions (FAQs)
What is Mach 1 in km/h at standard temperature?
At standard sea level (15°C), Mach 1 is approximately 1,225 km/h (661.5 kts / 340.3 m/s).
Why does the speed of sound decrease at high altitude?
Air temperature decreases with altitude up to the tropopause (-56.5°C), which lowers the speed of sound from 661 kts to ~573 kts.
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Calculations and mathematical logic on this page are grounded in published statutory rules, regulatory standards, and official government data published by the following bodies:
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