Speed of Sound Calculator
Sound travels faster in warm air.
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Speed of sound (m/s)
Speed of sound (m/s)
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Speed of sound (km/h)
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Speed of sound (mph)
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Distance to lightning (km)
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Speed of Sound Calculator by TheCalcTools
How the Speed of Sound Calculator works
Enter the air temperature.
Speed of sound in dry air is about 331.3 m/s at 0°C and rises with the square root of absolute temperature.
Enter the seconds between lightning and thunder to estimate how far away the storm is.
The formula
c = 331.3 × √(1 + T ÷ 273.15) m/sdistance = c × delay
Worked example
Using the default values shown in the calculator:
| Air temperature (°C) | 20 |
|---|---|
| Delay between flash and thunder (s) | 6 |
- At 20°C: c = 331.3 × √(1 + 20 ÷ 273.15) = 343.21 m/s.
- A 6-second delay puts the strike about 2.06 km away.
Result:
| Speed of sound (m/s) | 343.21 |
|---|---|
| Speed of sound (km/h) | 1,235.6 |
| Speed of sound (mph) | 767.7 |
| Distance to lightning (km) | 2.06 |
Frequently asked questions
What is the 'five seconds per mile' rule?
Thunder takes about 5 seconds to travel a mile, or 3 seconds per kilometre, so you can count seconds after lightning.
Does humidity matter?
Slightly: humid air carries sound a little faster. This tool uses dry air.
Sources and further reading
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This calculator gives estimates for information only. Check important results independently before you rely on them. See our disclaimer.