Speed of sound calculator
The speed of sound in air from temperature, with a conversion to kilometres per hour.
Fill in the fields and the result will appear here automatically.
Estimate sound speed in dry air for −80 to 80 °C. Additional rows convert to km/h and show time over 1 km and distance in 3 seconds. This assumes a uniform medium, not a ray path through wind and temperature layers.
How it works
Formula and logic
c=331.3√(1+t/273.15) m/s is the stated approximation at fixed composition and heat-capacity ratio. Thus km/h=3.6 c, time over 1 km=1000/c s and distance in 3 s=3 c m.
Example
At 20 °C the model gives 343.21 m/s,1235.57 km/h, about 2.914 s over 1 km and 1029.64 m in 3 s. At 0 °C it returns 331.3 m/s.
Fields and units
- Air temperature — °C
How to use
- — Enter air temperature, not the source temperature.
- — Distinguish speed relative to the medium from ground-relative speed in wind.
- — At constant speed distance=c·time; display rounding does not change the underlying calculation.
Method and limitations
- Calculation method
- Formula and logic
- Data or methodology source
- NASA: ideal-gas sound speed
- Limitation
- Approximate dry air with fixed gas parameters. Humidity and composition can change sound speed; there is no universal “under 1%” guarantee. Water, steel and nonuniform air need another model. Thunder-delay distance does not establish a safe lightning distance.
FAQ
Why does pressure not affect the speed of sound?
c=331.3√(1+t/273.15) m/s is the stated approximation at fixed composition and heat-capacity ratio. Thus km/h=3.6 c, time over 1 km=1000/c s and distance in 3 s=3 c m.
Why divide thunder delay in seconds by three to estimate kilometres?
Divide the delay in seconds, not the distance: approximately d in km ≈ delay/3. In the model, d = c·delay/1000. At 20 °C the model gives 343.21 m/s,1235.57 km/h, about 2.914 s over 1 km and 1029.64 m in 3 s. At 0 °C it returns 331.3 m/s. Approximate dry air with fixed gas parameters. Humidity and composition can change sound speed; there is no universal “under 1%” guarantee. Water, steel and nonuniform air need another model. Thunder-delay distance does not establish a safe lightning distance.
Does humidity matter?
Approximate dry air with fixed gas parameters. Humidity and composition can change sound speed; there is no universal “under 1%” guarantee. Water, steel and nonuniform air need another model. Thunder-delay distance does not establish a safe lightning distance.
What about water and steel?
About 1500 m/s in water and about 5900 m/s in steel — many times faster than in air, because those media are far less compressible. This calculation does not apply to them.