Speed of sound in air
Speed of sound in air from c ≈ 331.3 × √(1 + t/273.15): 331.3 m/s at 0 °C and 343.215 m/s at 20 °C, with a linear approximation 331.3 + 0.606t, a −20 to 100 °C reference table and the per-degree increment.
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Speed of sound
Computed for dry air — humidity raises the value slightly.
Enter a temperature to calculate the speed of sound
Speed: 0 · km/h: 0 · Per °C: 0
What this tool does
- Temperature-correct an ultrasonic rangefinder or level sensor with the measured air temperature.
- Check textbook values for a physics lab: 331.3 m/s at 0 °C and 343.2 m/s at 20 °C.
- Estimate delay: convert milliseconds into metres for echo, latency or speaker placement work.
Example
Input
25
Output
25 °C 时空气中的声速：346.129201 m/s 换算：1246.065125 km/h 公式（平方根式）：331.3 × √(1 + t / 273.15) 每升高 1 °C 增加约：0.579976 m/s 常用温度对照：-20 °C = 318.940594 m/s、0 °C = 331.3 m/s、15 °C = 340.275081 m/s、20 °C = 343.214623 m/s、25 °C = 346.129201 m/s、30 °C = 349.019442 m/s、40 °C = 354.729283 m/s、100 °C = 387.224258 m/s
At 20 °C sound travels 343.216 m/s (≈ 1235.578 km/h), gaining about 0.585 m/s per degree near 20 °C.
Frequently asked questions
Why 331.3 and not 331.5?
331.3 m/s is the 0 °C value from the ideal-gas relation c = √(γRT/M) with dry air: γ = 1.4, R = 8.314, M = 0.0289645 kg/mol. The 331.5 figure in some older texts differs by 0.06% and does not matter in practice.
How far apart are the square-root and linear forms?
Between −20 °C and 40 °C the linear 331.3 + 0.606t stays within 0.05% of the square-root form, i.e. under 0.2 m/s. Use the square root for lab reports, the linear form for quick field work.
Does humidity matter?
Slightly: at 20 °C going from 0% to 100% relative humidity raises the speed from 343.2 to about 344.5 m/s (+0.4%). This tool computes dry air, so its value is the lower bound.
What happens below −273.15 °C?
It reports an error. Absolute zero is the thermodynamic floor, and the expression under the square root would go negative.
What about solids and liquids?
Water is about 1480 m/s at 20 °C, steel about 5900 m/s and aluminium about 6300 m/s — far faster than air. This tool covers air only.
Keywords：声速计算speed of sound空气声速343 m/s超声波测距温度修正声速公式acoustic velocity