Joules to Electronvolts (J to eV)

1 joule equals 6.241509074×10¹⁸ electronvolts (rounded).

1 joule = 6.241509074×10¹⁸ electronvolts

How to convert joules to electronvolts

To convert joules to electronvolts, multiply the number of joules by 6.241509074×10¹⁸. The factor is rounded to 10 significant digits. To go the other way, multiply electronvolts by 1.602176634×10⁻¹⁹.

electronvolts = joules × 6.241509074×10¹⁸

Example: 10 joules = 6.241509074×10¹⁹ electronvolts.

The 'calorie' on food labels is really a kilocalorie. The thermochemical calorie (4.184 J) is used here unless marked IT.

About these units

Joule (J)

Metric (SI)Current unit

The SI unit of energy: the work done by a force of one newton over one meter, or one watt for one second.

James Prescott Joule was born in Salford on 24 December 1818, the son of a wealthy brewer, and later ran the family brewery while treating science as a serious hobby. In June 1845 he told a British Association meeting in Cambridge about his best-known experiment: a falling weight turned a paddle wheel inside an insulated barrel of water, and the water warmed up. Mechanical work turned into heat at a fixed rate, which supported energy conservation and undermined the caloric theory of heat.

The unit came later. On 23 August 1882 Carl Wilhelm Siemens proposed at a British Association meeting that a unit of heat equal to 10 million ergs be named the joule, and in 1889 the second International Electrical Congress adopted it alongside the watt. Joule died that same year. In 1948 the CGPM added that the joule should be preferred to the calorie as the unit of heat, and it entered the SI in 1960.

For scale, one joule is about the energy needed to lift an apple of roughly 102 g by one meter. A 56 g tennis ball moving at 6 m/s carries about one joule of kinetic energy.

The joule is the reference unit for energy on this site.

Sources: Wikipedia: Joule; Wikipedia: James Prescott Joule

Electronvolt (eV)

ScientificCurrent unit

Exactly 1.602176634×10⁻¹⁹ joules, the energy gained by an electron moving through one volt. Used in atomic and particle physics.

Particle physicists adopted this unit because a charged particle crossing a voltage V gains energy qV, so an electron accelerated through one volt in a vacuum gains exactly one electronvolt. Since the 2019 revision of the SI, the elementary charge is fixed, which makes 1 eV exactly 1.602176634 x 10^-19 J. The NIST appendix page still shows a rounded, non-exact value, reflecting the time before this redefinition. The unit is not part of the SI itself.

It suits the atomic world. Visible photons carry roughly 1.65 to 3.26 eV, green light at 532 nm is about 2.33 eV, and ionising hydrogen needs 13.6 eV. Molecular bonds are on the order of 1 to 10 eV each, and thermal motion at 20 degrees Celsius corresponds to about 0.025 eV. Particle masses are also quoted in eV/c squared, so the proton is about 938 million of them. Larger multiples such as keV, MeV and GeV extend the scale upward.

1 electronvolt = 1.602176634×10⁻¹⁹ joules (exactly).

Sources: Wikipedia: Electronvolt; NIST SP 811, Appendix B.8 (energy conversion factors)

Related conversions

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