Volts to Electron-Volts Calculator — eV, keV, MeV & Joules
Enter the accelerating voltage (in volts) and the particle's charge number to find the kinetic energy gained in electron-volts, kiloelectron-volts, megaelectron-volts and joules. Used in particle physics, electron microscopy and X-ray physics.
V
Kinetic energy gained by a charge q through potential V
- 1
Charge number
q = 1 = 1 - 2
Energy in electron-volts
q × V = 1 × 1,000 = 1,000Each elementary charge gains one eV per volt of potential difference.
How does this calculator work?
A particle with charge q (in elementary charges) accelerated through V volts gains E = q × V eV of kinetic energy. 1 eV = 1.602176634 × 10⁻¹⁹ J (exact, SI 2019). An electron through 1000 V gains 1000 eV = 1 keV = 1.602 × 10⁻¹⁶ J. Alpha particles (q = 2) gain twice the energy for the same voltage.
Formula
How this is calculated
An electron-volt (eV) is a unit of energy defined as the energy gained by a particle carrying one elementary charge (e = 1.602176634 × 10⁻¹⁹ C, exact under the 2019 SI redefinition) when it is accelerated through a potential difference of exactly one volt. By definition, a single electron accelerated through 1 V acquires 1 eV = 1.602176634 × 10⁻¹⁹ J of kinetic energy.
For any particle with charge number q (the number of elementary charges, e.g. q = 1 for an electron or proton, q = 2 for an alpha particle He²⁺, q = 3 for a Li³⁺ ion), the energy gained is E = q × V electron-volts, or equivalently E = q × e × V joules. The formula assumes the particle starts from rest and that relativistic effects are negligible — at electron energies above about 500 keV the particle reaches a significant fraction of the speed of light and a relativistic treatment is needed.
The eV is the natural unit for atomic, nuclear and particle physics because the energies involved are tiny fractions of a joule but convenient multiples of eV: chemical bond energies are a few eV, X-ray photons range from ~100 eV to ~100 keV, and the Large Hadron Collider accelerates protons to 6.8 TeV (6.8 × 10¹² eV). The WaveForm shown uses a logarithmic period count to illustrate how dramatically energy scales across these regimes.
Frequently asked questions
1 eV = 1.602176634 × 10⁻¹⁹ J exactly (SI 2019). Conversely, 1 J = 6.241509 × 10¹⁸ eV. The eV is far more convenient than joules for atomic and subatomic energies because the numbers involved in everyday particle physics are in the range of eV to TeV rather than 10⁻²⁰ to 10⁻⁷ joules.
No — the energy gained from the electric field depends only on the charge (q × V). The mass determines how fast the particle moves at that energy: a heavy alpha particle at 1 MeV moves much slower than an electron at 1 MeV. At relativistic speeds (above ~500 keV for electrons, ~500 MeV for protons) you need the relativistic kinetic energy formula rather than ½mv².
Visible light photons have energies of about 1.8 eV (red, 700 nm) to 3.1 eV (violet, 400 nm). Below that lies infrared and radio waves (meV to μeV); above it are UV (3–100 eV), X-rays (100 eV – 100 keV) and gamma rays (> 100 keV). An X-ray tube running at 100 kV produces photons with a maximum energy of 100 keV.
Also known as
TG we-Calculate Editorial Team. (2026). Volts to Electron-Volts Calculator — eV, keV, MeV & Joules [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/volts-to-electron-volts-calculator
TG we-Calculate Editorial Team. "Volts to Electron-Volts Calculator — eV, keV, MeV & Joules." TG we-Calculate. 2026. https://we-calculate.com/calculator/volts-to-electron-volts-calculator.
TG we-Calculate Editorial Team, "Volts to Electron-Volts Calculator — eV, keV, MeV & Joules," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/volts-to-electron-volts-calculator
@misc{wecalculate_volts_to_electron_volts_calculator, title = {Volts to Electron-Volts Calculator — eV, keV, MeV & Joules}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/volts-to-electron-volts-calculator}}, year = {2026}, note = {TG we-Calculate} }
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