Photon Energy
Calculator

A photon's energy depends only on its frequency (or equivalently, its wavelength), following E = h × f, where h is Planck's constant. Higher frequency, shorter wavelength light — like ultraviolet or X-rays — carries more energy per photon than lower frequency light like infrared or radio waves.

Frequency and wavelength are inversely related for light traveling at a fixed speed (c = f × λ), so a shorter wavelength implies a higher frequency. Since energy is proportional to frequency, shorter wavelengths always carry more energy per photon.

No — brightness (intensity) reflects the number of photons arriving per second, not the energy of each individual photon. A dim ultraviolet source can have far more energetic photons than an intensely bright red light, even though the red light delivers more total energy overall.

Individual photon energies are extremely small — on the order of 10⁻¹⁹ joules for visible light — because Planck's constant itself is minuscule. For this reason, results are often expressed in electronvolts (eV) instead of joules, since 1 eV equals about 1.602 × 10⁻¹⁹ J, a more convenient scale for atomic-level energies.

Wavelength should be entered in meters for the calculation to work correctly with standard SI constants, though the calculator typically accepts nanometers since visible light wavelengths (about 380–750 nm) are inconveniently small in meters. Double-check which unit the input field expects before entering a value.