Speed of Sound Calculator

How it works

Dry air: c = 331.3 √(1 + T/273.15) m/s (= √(γRT/M)) · fresh water (Marczak 1997): c = 1402.385 + 5.038813 T − 0.05799136 T² + 3.287156×10⁻⁴ T³ − 1.398845×10⁻⁶ T⁴ + 2.78786×10⁻⁹ T⁵ · sea water (Mackenzie 1981): c = 1448.96 + 4.591T − 0.05304T² + 2.374×10⁻⁴T³ + 1.340(S − 35) + 0.0163D + 1.675×10⁻⁷D² − 0.01025T(S − 35) − 7.139×10⁻¹³TD³ · T in °C, S in ‰, D in m

Sound is a pressure wave, and its speed depends on how stiff and how dense the medium is. In an ideal gas it depends only on temperature, so air carries sound about 0.6 m/s faster for every degree Celsius — 331 m/s at 0 °C and 343 m/s at 20 °C; pressure on its own makes no difference and humidity raises it only slightly. Water is far stiffer, so sound travels more than four times faster: about 1,482 m/s in fresh water at 20 °C. In the sea, speed rises with temperature, salinity and depth (pressure), which creates the SOFAR channel that lets whale calls cross oceans.

Worked example

In dry air at 20 °C: c = 331.3 × √(1 + 20/273.15) = 343.2 m/s (1,236 km/h, 1,126.0 ft/s). Sound takes 2.914 s to travel 1,000 m, and a 1 kHz tone has a wavelength of 0.343 m.

Sources: HyperPhysics — Speed of sound in air · NPL Technical Guides — Speed of sound in water (Marczak; Mackenzie equations)

Frequently asked questions