Photon Energy Calculator
Calculate the energy of a photon from its wavelength or frequency using the Planck-Einstein relation E = hf = hc/λ. Results are given in joules, electron volts (eV), and kilojoules per mole, with automatic identification of the electromagnetic spectral region.
The energy of a photon is directly proportional to its frequency and inversely proportional to its wavelength, as described by the Planck-Einstein relation: E = hf = hc/λ, where h is Planck's constant (6.626 × 10⁻³⁴ J·s), f is frequency, c is the speed of light (2.998 × 10⁸ m/s), and λ is wavelength.
This relationship is fundamental to quantum mechanics and explains many phenomena including the photoelectric effect, atomic emission spectra, and spectroscopy. Higher-frequency (shorter-wavelength) photons carry more energy — ultraviolet photons are energetic enough to break chemical bonds, while infrared photons cause molecular vibrations that we feel as heat.
In chemistry, photon energy calculations are essential for spectroscopy (UV-Vis, IR, NMR), photochemistry, and understanding electronic transitions in atoms and molecules. The energy per mole of photons tells chemists whether light of a given wavelength has sufficient energy to drive a photochemical reaction, break a specific bond, or excite an electron to a higher orbital.