1 electronvolt equals exactly
1,602 × 10⁻¹⁹ Joules
The electronvolt (eV) is defined as the energy gained by a single electron when accelerated through a potential difference of one volt, and is used to describe energies at the atomic and subatomic level. Its exact value in Joules, 1.602176634 × 10⁻¹⁹, is one of the fundamental physical constants, fixed by definition since 2019.
To convert a measurement from electronvolts to Joules, multiply by 1.602176634 × 10⁻¹⁹:
To convert from Joules to electronvolts, perform the inverse operation, dividing by the same factor:
The electronvolt is the preferred unit in particle physics, nuclear physics, and quantum chemistry, where atomic binding energies, ionization energies, or energies released in nuclear reactions are described: all quantities so small that expressing them in Joules would always require scientific notation.