Wavelength Calculator

Convert between frequency, wavelength, wave speed and photon energy for light, sound or a custom medium.

Waves and photons

Medium Wave speed (m/s)

Known quantity Value

Frequency: —

Wavelength: —

Wave speed: —

Photon energy: —

Note: —

The tool uses the wave equation, speed equals frequency times wavelength, and the photon relation, energy equals Planck constant times frequency.

Common questions about the free online wavelength calculator.

Choose frequency as the known quantity, type the value, and the tool divides the wave speed by the frequency to give the wavelength.

Wave speed equals frequency times wavelength, so any one of the three quantities can be found from the other two values.

Photon energy is the Planck constant times the frequency, which is the same as the Planck constant times the speed of light divided by wavelength.

Light in vacuum uses 299792458 metres per second and sound in air uses about 343 metres per second, and any custom speed can be typed.

It is 6.62607015 times ten to the power minus 34 joule seconds, the constant that links photon energy to frequency.

Yes. Sound follows the same wave equation, but the photon energy value only has meaning for electromagnetic radiation.

Wavelengths appear in metres, nanometres or kilometres as needed, and energies appear in joules and in electronvolts.

Yes. Choose photon energy as the known value and the tool finds the frequency first and then the wavelength from the wave speed.

The constants used are the exact SI values, and results are shown to six decimal places or in scientific notation.

No, the wavelength calculator runs entirely in your browser and every conversion happens locally.

Last updated: October 10, 2026