Enter a temperature and choose your medium (air or water) to calculate the speed of sound. Results are shown in m/s, km/h, mph, ft/s, and knots — all at once. Switch between °C and °F using the unit selector.
Speed of Sound (m/s)
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Speed (km/h)
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Speed (mph)
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Speed (ft/s)
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Speed (knots)
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Temperature (K)
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For dry air, the speed of sound is calculated using c = √(γ·R·T/M), where γ (gamma) is the adiabatic index (~1.4 for air), R is the molar gas constant (8.3145 J·mol⁻¹·K⁻¹), T is the absolute temperature in Kelvin, and M is the molar mass of air (~0.0289645 kg/mol). A simpler approximation is c ≈ 331.3 × √(T/273.15) m/s, or c ≈ 331.3 + 0.606 × t m/s where t is in °C.
The speed of sound increases as temperature rises. In air, for every 1°C increase in temperature, the speed of sound increases by approximately 0.6 m/s (about 0.606 m/s to be precise). This is because warmer air molecules have more kinetic energy and collide more frequently, allowing sound waves to propagate faster.
At 20°C (68°F) — roughly room temperature — the speed of sound in air is approximately 343 m/s (1,235 km/h or 767 mph). At 0°C (32°F), it drops to about 331 m/s. These values apply to dry air at standard atmospheric pressure.
The speed of sound in water is much faster than in air — approximately 1,480–1,500 m/s at 20°C (about 4 times faster than in air). It increases with temperature: at 0°C it is around 1,403 m/s, and at 100°C it reaches around 1,543 m/s. Water's higher density and bulk modulus allow sound to travel significantly faster.
Sound travels as a mechanical wave, meaning it propagates through the collision of molecules. Water molecules are much more tightly packed than air molecules, so they transfer vibrational energy more efficiently. Even though water is denser, its incompressibility (high bulk modulus) more than compensates, resulting in a much higher speed of sound.
A widely used empirical formula for the speed of sound in fresh water is c ≈ 1402.4 + 5.01·T − 0.055·T² + 0.00022·T³ m/s, where T is the temperature in °C. This formula is valid for temperatures between 0°C and 100°C at standard atmospheric pressure.
Mach 1 is defined as the speed of sound in the surrounding medium. Because the speed of sound depends on temperature, Mach 1 is not a fixed speed — at sea level and 20°C, Mach 1 ≈ 343 m/s (767 mph), while at high altitudes where temperatures are much lower, Mach 1 is slower. An aircraft flying at Mach 2 travels at twice the local speed of sound.
At constant temperature, air pressure has negligible effect on the speed of sound in ideal gases — the two variables cancel out in the formula. Humidity does have a small effect: moist air is slightly less dense than dry air (water vapor molecules are lighter than N₂ or O₂), so humid air carries sound marginally faster. This effect is small compared to temperature changes.