1 Joule equals about
6,242 × 10¹⁸ electronvolts
The Joule is the energy unit of the International System, used for macroscopic amounts of energy, while the electronvolt (eV) is an extremely small unit used in particle physics. Given the enormous difference in scale, a single Joule equals an astronomical number of electronvolts: about 6.242 × 10¹⁸.
To convert a measurement from Joules to electronvolts, simply divide the value by 1.602176634 × 10⁻¹⁹:
To convert from electronvolts to Joules, perform the inverse operation, multiplying by the same factor:
This conversion concretely illustrates how small the electronvolt is compared to the Joule, a unit of energy we use every day. It is useful in physics for expressing macroscopic energies (calculated in Joules) on the scale used for subatomic particles, for example to compare the energy of a photon with that of a macroscopic object.