Electron-volt to Joule Converter

The joule is the SI unit of energy, sized for the macroscopic world: lifting an apple one metre costs about one joule. For particle energies it is far too large — an electron's binding energy would be written with eighteen zeros after the decimal point. The electronvolt fixes that: it is the energy an electron gains crossing a potential difference of one volt.

Enter the value and the direction, and the page converts. The factor is the elementary charge, which since the 2019 SI redefinition has an exact value by definition: 1.602176634 times ten to the minus nineteen. It is no longer a measurement with uncertainty — it is a fixed constant, and the coulomb is now defined from it.

In practice each field uses a different multiple. Chemistry and solid-state physics work in electronvolts for binding energies and band gaps. Nuclear physics uses mega-electronvolts, and particle physics giga and tera — the per-beam energy at the largest accelerator in operation sits in the teras. Choosing the multiple is what keeps the numbers readable without scientific notation.