Speed of sound in air by temperature
Enter the air temperature in °C to get the speed of sound. Useful for judging lightning distance and for echo and acoustics experiments.
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How to use it
- Enter air temperature.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
v = 331.3 × √(1 + T / 273.15), where T is the temperature in °C and 331.3 m/s is the speed of sound in dry air at 0 °C.
Example
Inputs: Air temperature = 20 °C. Result: Speed of sound: 343.21 m/s; In km/h: 1,235.6 km/h; In ft/s: 1,126 ft/s.
Limits and caveats
- For dry air. Humidity raises the speed slightly, by less than 1% in normal conditions.
- Wind is not included; it adds to the speed downwind and subtracts upwind.
Questions about this tool
How do I estimate lightning distance?
Multiply the seconds between flash and thunder by the speed of sound; about 3 seconds means roughly one kilometer.
Does air pressure change the speed of sound?
In an ideal gas pressure alone has no effect; temperature is what matters.
How fast is sound on a 45 °C Gulf summer day?
About 357.5 m/s, roughly 14 m/s faster than at 20 °C.