Convert between the electronvolt and other major units of mass.
Convert between the electronvolt and other major units of energy.
A unit of energy, equal to the amount of kinetic energy acquired by an electron accelerated by passing through a potential difference of one volt, determined experimentally to be about 1.602 176 × 10⁻¹⁹ 1 eV = 1.602 176 634 × 10⁻¹⁹ Jjoules. For a more precise value, consult the most recent CODATA table. Symbol, eV, but ev was used earlier². The unit was introduced in 1912¹ as the “equivalent volt”.
Electronvolt has variously been spelled as electron volt, electron-volt and electronvolt. We use the last, because it is the spelling in current (2025) use by NIST and BIPM
The electronvolt is often used to express the mass of atomic particles, which is possible through Einstein’s famous equation expressing the equivalence of mass and energy, e = mc². One electronvolt of energy is equivalent to about 1.073 544 × 10⁻⁹ unified atomic mass units. Wikipedia has an excellent entry on the electronvolt, which treats how it can be a unit of mass or energy.
Although the electronvolt is not an SI unit, the SI prefixes are used with it. The prefix B (for billion, American style) has also been used, but it was deprecated by the IUPAP and is not currently in use.
1. O.W. Richardson and K.T. Compton.
The photoelectric effect.
Philosophical Magazine, series 6, vol 24, no. 142, pages 575-594. 583 (Oct. 1912).
2. National Research Council.
A Glossary of Terms in Nuclear Science and Technology.
New York: American Society of Mechanical Engineers, 1955.
Pages 56 and 59.
Since the atom can receive energy by the impact of an electron, the energy of which may be expressed as the voltage difference through which it is accelerated, the “equivalent” volt (1.591 × 10⁻¹² erg) forms a convenient energy unit.
Transactions of the Illuminating Engineering Society of London, vol 1, page 51 (1936).
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Last revised: 16 February 2017.
