Wave Speed Calculator

How it is calculated

The tool multiplies frequency by wavelength: v = f × λ, where f is the frequency in hertz (cycles per second) and λ is the wavelength in metres. The product is a speed in metres per second, rounded to two decimals. Both fields are required. The tool does not check the sign, so a negative number simply gives a negative speed. It works for any wave type, sound, light, radio or water waves, because the relation is the same; what changes is the medium. Convert kilohertz, megahertz, centimetres or nanometres to hertz and metres first, otherwise the result is off by that factor. The speed also tells you nothing about the medium unless you compare it to the known speed there.

Common mistakes

• Typing the frequency in kHz or MHz without converting. 100 MHz must be entered as 100000000, otherwise the speed is a million times too small.
• Entering the wavelength in centimetres or nanometres. The result is only in m/s if the wavelength is in metres.
• Entering the period or angular frequency (rad/s) instead of frequency in hertz. Angular frequency is 2π times larger and makes the speed 6.28 times too big.
• Using a wavelength measured in one medium with a frequency from another. When a wave crosses into a new medium the frequency stays the same but the wavelength changes.
• Treating the result as a constant of the wave source. The speed is set by the medium, not by the source, so the same source gives different speeds in air and in water.