Volt to Electron Volt Calculator

The electron volt (eV) is the standard unit of energy used in particle physics, atomic physics, and semiconductor engineering. It is defined as the amount of kinetic energy gained by a single electron when it is accelerated through an electric potential difference of exactly one volt in a vacuum. Because the elementary charge of an electron is 1.602176634×10⁻¹⁹ coulombs, one electron volt equals 1.602176634×10⁻¹⁹ joules. The defining equation is E = qV, where E is energy in joules, q is the charge of the particle in coulombs, and V is the voltage in volts. For a single electron, q = e (the elementary charge), so the energy gained in joules is always the voltage multiplied by 1.602176634×10⁻¹⁹. Crucially, the numeric value of the energy in electron volts is identical to the voltage in volts — 12 volts accelerates an electron to 12 eV, and 1 000 volts gives it 1 000 eV (1 keV). This elegant one-to-one mapping is what makes the electron volt such a practical unit. Electron volts are preferred in atomic and nuclear sciences because joules are an inconveniently large unit at subatomic scales. A single photon of visible light carries only about 2–3 eV, the ionisation energy of hydrogen is 13.6 eV, a typical X-ray photon carries 100 to 100 000 eV, and gamma-ray photons exceed 100 keV. At the other end of the scale, modern particle accelerators push protons to billions of electron volts (GeV) and even trillions (TeV). All of these numbers would be unwieldy as multiples of 10⁻¹⁹ joules. In semiconductor engineering, eV describes band gaps — the energy difference between the valence band and the conduction band of a material. Silicon has a band gap of 1.12 eV, gallium arsenide about 1.42 eV, and gallium nitride roughly 3.4 eV. These values determine which wavelengths of light a material can absorb or emit, making them essential for designing solar cells, LEDs, and laser diodes. The voltage at which a forward-biased LED turns on is approximately equal to its band gap in eV. In electron microscopes, the accelerating voltage determines beam resolution. A 100 kV electron has a de Broglie wavelength orders of magnitude smaller than visible light, enabling sub-nanometer imaging. In mass spectrometers, the ratio of an ion's mass to its charge (m/z) is calibrated against the accelerating voltage in electron volts. Understanding the volt-to-eV relationship is therefore not merely a unit-conversion exercise — it links macroscopic electrical engineering quantities to the quantum mechanical behaviour of individual particles.