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Speed of Sound Calculator

Find the speed of sound in air.

Result

343.21 m/s

How it is calculated

Sound travels faster in warmer air. The tool uses v = 331.3 × √(1 + T / 273.15), with T the air temperature in °C and v in metres per second. 331.3 m/s is the speed at 0 °C and 273.15 is the offset from 0 °C to absolute zero. The square root comes from the fact that speed depends on the square root of absolute temperature. The formula is for dry air; humidity raises the speed slightly. Any temperature above −273.15 °C is accepted, though results far outside normal weather are only mathematical. Water, steel and other media are very different.

Worked example

The air temperature is 20 °C. First, T / 273.15 = 20 / 273.15 ≈ 0.0732, so 1 + 0.0732 = 1.0732. The square root is about 1.0360. Multiply by 331.3 and the speed of sound is 343.21 m/s, or about 1,235 km/h. At 0 °C it would be 331.3 m/s, so each extra degree adds roughly 0.6 m/s.

Try this example →

Common mistakes

  • Entering the temperature in °F or kelvin; the field uses °C only.
  • Applying the result to water or solids, where sound is several times faster.
  • Assuming the speed changes with air pressure; at a fixed temperature it does not (in ideal gas terms).
  • Forgetting that the value is in m/s, then comparing it to km/h speed limits.
  • Using the value to time lightning at a different temperature than the one entered.

About this calculator

This calculator uses v = 331.3 × √(1 + T/273.15) m/s, the standard approximation for how fast sound travels through dry air at temperature T (°C). It comes from the adiabatic relationship v = √(γRT/M), where γ is the ratio of specific heats for air and M its molar mass — since neither humidity nor pressure changes the result much at normal conditions, temperature alone is enough to get a good estimate.

Acousticians and audio engineers use it to time delay speakers and align microphone arrays, aviation and artillery calculations rely on it for sound-ranging (like the “flash-to-bang” thunder count), and physics students use it to check how pitch and echo timing shift between a cold morning and a hot afternoon.

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