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Speed of Sound & Mach Number Calculator

Calculate Mach number, speed of sound in air (m/s, km/h, kts), and flight speed regimes.

Input Parameters

Calculation Results

Speed of Sound (Mach 1.0)
661.6 kts (1225.3 km/h)
Current Mach Number
Mach 0.68
Flight Speed Regime
Subsonic
Speed of Sound in m/s & mph
340.3 m/s | 761.3 mph
Summary: At 15°C, the Speed of Sound is 661.6 kts (1225.3 km/h). An airspeed of 450 kts equals Mach 0.68 (Subsonic).
Step-by-Step Calculation Solution
1.Absolute Temperature T = 15°C + 273.15 = 288.15 K
2.Speed of Sound a = 20.05 × √T = 20.05 × √288.15 = 340.3 m/s (661.6 kts)
3.Mach Number = TAS / a = 450 / 661.6 = Mach 0.68

Formula & How Speed of Sound & Mach Number Calculator Works

Mathematical Formula
Speed of Sound a = 20.05 × √(T_Kelvin) m/s | Mach = TAS / a

The speed of sound depends primarily on absolute air temperature. At standard sea level (15°C / 59°F), the speed of sound is 661.5 kts (1,225 km/h / 340.3 m/s). In cold cruising altitudes (-56.5°C), it drops to ~573 kts.

How to Calculate Speed of Sound & Mach Number Calculator (Step-by-Step)
  1. Enter Ambient Air Temperature (°C): Input your target parameter value.
  2. Enter True Airspeed (TAS - kts): Input your target parameter value.
  3. Apply Formula: Calculate using Speed of Sound a = 20.05 × √(T_Kelvin) m/s | Mach = TAS / a.
  4. Review Results: View exact computed answers, metrics, and worked mathematical proofs.
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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.

Official Regulatory & Government Data Sources

Authoritative Standards & Verified Reference Citations

Independent & Verified

Calculations and mathematical logic on this page are grounded in published statutory rules, regulatory standards, and official government data published by the following bodies:

Australian Government Data Portal (data.gov.au)Government
Commonwealth of Australia

Open government data, scientific datums, and public sector mathematical reference datasets.

data.gov.au
National Measurement Institute (NMI)Government
Australian Department of Industry, Science and Resources

Australia's national authority on physical, chemical, and biological metric measurement standards.

www.industry.gov.au/national-measurement-institute

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