Calculate photon energy from wavelength or frequency using the Planck relation.
Photon energy is inversely proportional to wavelength, so blue light carries more energy per photon than red. Visible photons are around 2 to 3 electronvolts, which is why that range drives photochemistry. The electronvolt is the natural unit here because it matches the scale of atomic and molecular energy levels.
Photon Energy
E = h f = h c ÷ λ
E = h f = h c ÷ λ Photon energy is inversely proportional to wavelength, so blue light carries more energy per photon than red. Visible photons are around 2 to 3 electronvolts, which is why that range drives photochemistry.
The electronvolt is the natural unit here because it matches the scale of atomic and molecular energy levels.
This calculator takes 1 input: Wavelength. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.