What is the speed of sound at 20°C?

In dry air at 20°C the speed of sound is about 343 m/s (1235 km/h or 767 mph). It rises by roughly 0.6 m/s for each degree Celsius increase.

What formula is used?

The accurate form is c = 331.3 × √(1 + T/273.15) m/s for dry air, where T is the temperature in °C. The familiar linear approximation c ≈ 331.3 + 0.606·T is also shown.

How do I estimate lightning distance?

Count the seconds between the lightning flash and the thunder, then divide by about 3 to get the distance in kilometres (or divide by 5 for miles), because sound travels roughly 343 m per second.

Speed of Sound Calculator

Speed of sound in air at any temperature, plus travel time.

Speed of sound calculator

The speed of sound in dry air depends mainly on temperature: c = 331.3 × √(1 + T/273.15) m/s, giving about 343 m/s at 20°C. A handy linear approximation is c ≈ 331.3 + 0.606·T.

Enter a temperature to get the speed in m/s, km/h and mph, then enter a distance to find how long sound takes to travel it — useful for estimating how far away a lightning strike is.

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