Wavelength and Frequency Calculator
Enter any two of wave speed, frequency and wavelength. The speed starts as the speed of light, and you can change it for sound or water waves.
The speed of light in a vacuum is 299,792,458 m/s. Sound in air at 20 °C is about 343 m/s, and in water about 1,480 m/s. Fill in two of speed, frequency and wavelength and leave the one you want to find empty. The answer appears as you type, in the unit shown next to its box.
Worked examples
FM radio
100 MHz at the speed of light
2.998 m
299,792,458 / 100,000,000.
Concert A
440 Hz in air at 343 m/s
0.7795 m
343 / 440.
About Wavelength and Frequency Calculator
Every wave obeys one simple rule: the speed equals the frequency multiplied by the wavelength. For light and radio waves the speed is that of light, 299,792,458 metres per second in a vacuum, so a higher frequency means a shorter wavelength. A station on 100 megahertz has a wavelength of about three metres, while visible green light at 540 terahertz has a wavelength of 555 nanometres. This calculator solves for any one of speed, frequency and wavelength.
Sound uses the same rule but at a much lower speed, about 343 metres per second in air at 20 degrees Celsius. A note of 440 hertz has a wavelength of nearly 0.78 metres. Change the speed box to suit the medium. When the speed is that of light, the page also gives the photon energy using the Planck constant, in joules and electronvolts, and the wave number.
How to use Wavelength and Frequency Calculator
- Check the wave speed, which starts as the speed of light.
- Enter the frequency, or the wavelength, and leave the other empty.
- Choose units such as megahertz, nanometres or kilometres.
- Read the missing value and, for light, the photon energy.
Common uses
- Finding the wavelength of a radio station or Wi-Fi signal
- Converting a colour of light between nanometres and terahertz
- Working out the wavelength of a musical note
- Checking the size of an antenna as a fraction of the wavelength
Frequently asked questions
What is the wave equation?
Wave speed equals frequency times wavelength (v = f x lambda). It applies to sound, light, water waves and waves on strings.
What speed should I use for sound?
About 343 metres per second in air at 20 degrees Celsius, and about 1,480 in water. Sound is faster in warmer air.
How is photon energy found?
It is the Planck constant, 6.62607015e-34 joule seconds, multiplied by the frequency. Green light at 500 nanometres carries about 2.48 electronvolts.
Why do radio waves in a cable travel slower?
Waves in a cable or glass travel at a fraction of the speed in a vacuum, called the velocity factor. Enter the right speed to match.