What is an electron volt?
An electron volt (eV) is a unit of energy equal to the kinetic energy gained by a single elementary charge (such as an electron) when it is accelerated through a potential difference of one volt. It is a convenient unit in atomic, nuclear, and particle physics because it avoids working with very small numbers of joules.
How this calculator works
The energy gained is given by E = q × V, where q is the charge in units of the elementary charge and V is the potential difference in volts. Because one electron volt is defined as the energy from exactly one elementary charge crossing one volt, the numeric value in eV equals the number of elementary charges multiplied by the voltage. The calculator also converts that result into attojoules (1 eV = 0.1602176634 aJ = 1.602176634 × 10⁻¹⁹ J) and into keV and MeV for convenience.
This tool is for general physics education and estimation. It assumes charges are accelerated through the full potential difference with no other energy losses.