🌈 Frequency of Light Calculator
Enter a wavelength to calculate the corresponding frequency and photon energy of light or other electromagnetic radiation.
Wavelength, frequency, and energy
Light and other electromagnetic radiation can be described by wavelength, frequency, or photon energy, and all three are directly related to each other through fundamental physical constants.
The formula
Frequency is found from the wave equation c = fλ, rearranged as f = c ÷ λ, where c is the speed of light. Photon energy then follows from Planck’s relation, E = hf, where h is Planck’s constant, giving the energy of a single photon of that frequency.
This treats light as traveling through vacuum, where its speed is exactly 299,792,458 m/s; light travels slower in a medium like glass or water, which changes wavelength (but not frequency or photon energy) accordingly. This calculator is for general physics education.