The electronvolt — energy at the atomic scale
One electronvolt is the energy an electron gains falling through 1 volt. That gives every particle physics energy a direct link to the voltage on the accelerator.
The electronvolt is not a joule and its size is not memorable — 1.602 × 10⁻¹⁹ J. But once you accept it as the natural unit for one electron falling through one volt, every atomic and nuclear energy fits into a simple ladder: chemistry at eV, X-rays at keV, nuclear reactions at MeV, and colliders at TeV.
The exact factor
1 eV = 1.602176634 × 10⁻¹⁹ J (exact since 2019 redefinition) > 1 keV = 10³ eV; 1 MeV = 10⁶ eV; 1 GeV = 10⁹ eV; 1 TeV = 10¹²eV > 1 eV/particle = 96.485 kJ/mol (chemistry conversion)
The energy ladder
Hydrogen ionisation: 13.6 eV. Visible photon: 1.6–3.1 eV. Chemical bonds: 1–10 eV. X-ray photon: 1–100 keV. Nuclear binding per nucleon: ~8 MeV. Muon rest mass: 106 MeV. Proton rest mass: 938 MeV. Higgs boson: 125 GeV. LHC per-proton beam energy: 6.5 TeV.
Mass and energy in the same unit
Particle physicists write masses in eV/c² because E = mc². The electron rest mass is 511 keV/c², the proton 938 MeV/c². The 'c²' is often dropped in speech ("a 125-GeV Higgs") because everyone knows what is meant. This convention lets you read a particle-physics paper without switching between joules, kilograms and eV.
Worked example — an X-ray from a copper anode
The Kα emission of copper is 8.04 keV = 1.289 × 10⁻¹⁵ J per photon = 1.541 Å wavelength. A dental X-ray tube running at 70 kV produces bremsstrahlung with maximum photon energy 70 keV. Both are directly connected to the tube voltage — which is exactly why the unit was invented.
The five-second recap
1 eV = 1.6 × 10⁻¹⁹ J. Atoms live at eV. Nuclei live at MeV. LHC lives at TeV. And mass in eV/c² is just energy divided by c².
Try the converters mentioned in this article
FAQ
What is 1 eV in kelvin?+
kT = 1 eV when T = 11,605 K. Room temperature (300 K) corresponds to about 25.7 meV per particle — a useful anchor in semiconductor physics.
How does LHC compare to a lightning bolt?+
A lightning bolt has ~10⁹ J of energy. LHC beam: 6.5 TeV per proton × 3 × 10¹⁴ protons = 3.1 × 10⁸ J — roughly a third of a lightning bolt, but focused on a beam 20 µm across.
Is eV an SI unit?+
No, but 'accepted for use with the SI'. Its value in joules is exact since 2019.
This article was written by The Turbo Unit Converter engineering desk (Physics) and last reviewed on 2026-06-28 against NIST SP 811 and the BIPM SI Brochure. Read our full editorial policy.