Calculates the speed of sound in dry air from temperature, using a widely used linear approximation.
How it works
Air temperature in Celsius is multiplied by a fixed coefficient and added to the formula’s reference speed at 0°C.
What this does not include
This approximation is for dry air at sea-level pressure — humidity and altitude both affect the actual speed of sound somewhat, which this simplified formula doesn’t account for.
How to use this calculator
- Enter the air temperature.
A worked example
Air at 25 °C, using the linear dry-air approximation:
v = 331.3 + (0.606 × 25) = 331.3 + 15.15 = 346.45 m/s
The same formula at other temperatures shows how much the “speed of sound” actually moves:
| Air temperature | Speed of sound |
|---|---|
| −10 °C | 325.24 m/s |
| 0 °C | 331.30 m/s |
| 20 °C | 343.42 m/s |
| 25 °C | 346.45 m/s |
Between a cold morning and a warm afternoon, sound can pick up around 20 m/s — which is why a single quoted figure is always tied to a stated temperature.
What the variables mean
| Variable | Meaning | Value used |
|---|---|---|
| 331.3 | Reference speed in dry air at 0 °C, in m/s | Fixed |
| 0.606 | How much the speed rises per °C, in m/s | Fixed |
| T | Air temperature in degrees Celsius | Your input |
Edge cases worth knowing
This is a linear approximation, and the real relationship is not linear. The speed of sound actually varies with the square root of absolute temperature; the straight-line formula used here is an excellent fit across ordinary ambient temperatures and drifts from the exact value at temperature extremes.
Altitude changes the answer less than you would expect. Because the speed of sound in an ideal gas depends on temperature rather than pressure, it is the temperature drop with altitude that slows sound at height — not the thinner air itself.
This is air only. Sound travels far faster through water and faster still through solids, and those media are not modelled by this formula.
Frequently asked questions
Why does sound travel faster in warmer air?
Warmer air molecules move faster and collide more often, transmitting the pressure waves that make up sound more quickly than in cooler, slower-moving air.
Why is 343 m/s often quoted as “the” speed of sound?
It’s the speed at 20°C, a common reference room temperature — the actual speed changes with temperature, as this calculator shows.
Does humidity affect the speed of sound?
Yes, slightly — moist air is less dense than dry air at the same temperature and pressure, which very slightly increases the speed of sound, an effect this dry-air approximation doesn’t capture.
