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Sound Wavelength Frequency Calculator

Enter a frequency and the speed of sound to find the wavelength.

Result

0.7795 m
77.95 cm
2.273 ms

How it is calculated

The wavelength is the distance sound travels during one cycle: λ = v ÷ f, with v the speed of sound in m/s and f the frequency in hertz. If the speed field is empty, v = 343 m/s, the usual value for air at about 20 °C. The tool also gives the period, the time of one cycle: T = 1 ÷ f, in milliseconds (T = 1000 ÷ f).

The wavelength is shown in metres with four decimals and in centimetres with two decimals; the period with three decimals. Frequency and speed must both be greater than zero. For another medium or temperature, type the speed yourself, for instance about 1480 m/s for water. Higher frequency means a shorter wavelength and a shorter period, and the speed only changes the wavelength, not the period.

Worked example

Take the note A4 at 440 Hz in air with the default 343 m/s. Wavelength: 343 ÷ 440 = 0.7795 m, which is 77.95 cm. Period: 1 ÷ 440 = 0.002273 s, or 2.273 ms. So each cycle of this tone lasts a little over two milliseconds and spans about 78 cm in the room.

Try this example →

Common mistakes

  • Entering the frequency in kilohertz. 2 kHz must be typed as 2000, otherwise the wavelength comes out 1000 times too large.
  • Using 343 m/s for every case. In water or on a very hot day the speed is different, and the wavelength shifts by the same proportion, so enter the right speed.
  • Confusing wavelength with period. The wavelength is a length in metres, the period a time in milliseconds, and the speed of sound does not change the period.
  • Typing the speed in km/h or mph. The field expects metres per second, so convert first.
  • Expecting an exact room-mode answer. This is the free-field wavelength; half or quarter of it is often what matters for standing waves and bass traps, and the tool does not divide it for you.

About this calculator

Sound wavelength follows the basic wave relation λ = v / f, where v is the speed of sound through the medium and f is the frequency in hertz. In dry air at 20°C, v is commonly taken as 343 m/s, though it rises with temperature and differs substantially in water (~1480 m/s) or solids.

The period of the wave — the time for one complete cycle — is simply 1/f, and together with wavelength it fully describes a pure tone's oscillation in space and time.

These figures matter for acoustic design: room dimensions and bass trap placement are chosen relative to the wavelengths of problem frequencies, loudspeaker and microphone spacing is set relative to wavelength to avoid interference, and musical instrument and organ pipe lengths are tuned using the same λ = v/f relation.

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Comments (1)

  • Editorial team

    The 343 m/s default assumes about 20 degrees Celsius. In air the speed rises by roughly 0.6 m/s for every degree, so a warm stage or a hall at 30 degrees is closer to 349 m/s, and the wavelengths grow by the same proportion. Type your own speed in the field when the temperature is far from 20. What temperature and frequency range are you designing around?

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