Sound Wavelength Calculator
The wavelength of a sound wave is the physical distance between successive compressions (or rarefactions) in the medium. It is linked to frequency by the wave equation: wavelength = speed of sound / frequency. At 20 degrees C in air, the speed of sound is 343 m/s. Knowing the wavelength is essential for room acoustics design, speaker placement, noise control engineering, and understanding why low-frequency sounds diffract around obstacles while high-frequency sounds travel in tighter beams. Enter any frequency to find the wavelength in metres and feet.
Sound wavelength formula
λ = c / f
Where c is the speed of sound in m/s and f is frequency in Hz. The result is wavelength in metres.
Wavelength at common frequencies
- 20 Hz (bass limit): 17.15 m
- 100 Hz: 3.43 m
- 1,000 Hz (1 kHz): 0.343 m
- 4,000 Hz: 0.086 m
- 20,000 Hz (treble limit): 0.017 m
Frequently asked questions
What is the speed of sound in air?
At 20 degrees C (68 F) and standard atmospheric pressure, the speed of sound in air is approximately 343 m/s. It increases by about 0.6 m/s per degree Celsius rise in temperature. This calculator uses 343 m/s as the standard value.
Why does wavelength matter in acoustics?
Wavelength determines how sound interacts with objects and room dimensions. A surface needs to be at least a quarter-wavelength in size to provide significant diffraction or absorption. Bass frequencies have long wavelengths (e.g. 100 Hz is 3.43 m) and are difficult to absorb, which is why bass traps are large.
What is the wavelength of 1 kHz in air?
At 1,000 Hz, wavelength = 343 / 1000 = 0.343 m (34.3 cm). This is a common reference point in architectural acoustics.
How does wavelength affect speaker placement?
Placing two speakers with the same signal less than half a wavelength apart causes constructive/destructive interference. At 100 Hz, half a wavelength is about 1.7 m, so two subwoofers closer than that will couple. At 10 kHz, half a wavelength is only 1.7 cm.
Does the formula change in other media?
Yes. The speed of sound changes with the medium: water is approximately 1,480 m/s, steel approximately 5,100 m/s. Simply substitute the appropriate speed of sound into the same formula: wavelength = speed / frequency.
Official sources
- NIST: NIST physical constants.
- OpenStax University Physics Vol. 1, Chapter 17: Sound.
- AES: Audio Engineering Society.
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.