Electronvolt Converter
An energy in electronvolts expressed every way a physicist uses it — joules, temperature, frequency, wavelength, wavenumber and mass equivalent — with the constants that link them.
The electronvolt is the energy an electron gains across one volt: 1.
How the electronvolt converter works
The electronvolt is the energy an electron gains across one volt: 1.602 × 10⁻¹⁹ joules. Physics uses it as a universal currency because every other quantity converts through a fundamental constant — energy over Boltzmann's constant is a temperature, over Planck's a frequency, and over c² a mass. One eV is 11,600 kelvin, 242 terahertz, 1,240 nanometers, or 1.78 × 10⁻³⁶ kilograms.
Those are the numbers that tell you whether a photon is infrared, whether a gas is a plasma, or what a particle accelerator can create.
Formula: E = hf = hc/λ = k_B T = mc²
Worked examples
| Inputs | Energy (eV) | Note |
|---|---|---|
| One electronvolt | 1.0000e+0 | 11,600 K, 1,240 nm |
| Room temperature | 2.5000e-2 | about 290 K |
| An electron's rest energy | 5.1100e+5 | 9.1 × 10⁻³¹ kg |
FAQFrequently asked questions
What is an electronvolt?
The energy an electron gains crossing a potential of one volt: 1.602 × 10⁻¹⁹ joules. Chemistry works in eV, nuclear physics in MeV, particle physics in GeV and TeV.
How can an energy be a temperature?
Through Boltzmann's constant: the typical thermal energy of a particle at temperature T is about k_B T. One eV corresponds to 11,600 K; room temperature is 25 meV.
How can an energy be a mass?
Through E = mc². Particle masses are quoted in MeV or GeV for exactly this reason: the electron is 0.511 MeV, the proton 938.
What is a wavenumber?
Reciprocal wavelength in cm⁻¹, the unit of infrared spectroscopy. One eV is about 8,066 cm⁻¹.
Why 1,240?
Because hc in eV·nm is 1,239.84. Divide it by an energy in eV and you have the photon's wavelength in nanometers — the most-used shortcut in optics.
Where these figures come from
- NIST — CODATA 2018 fundamental physical constants — G, g₀, R, c
- NIST Special Publication 811 — Guide for the use of the International System of Units — unit conversions
- The Engineering ToolBox — material properties — specific heats, expansion coefficients, densities
- National Institute of Standards and Technology — the US measurement authority
Last checked: September 2026. Constants are the CODATA 2018 values; formulas are the standard textbook forms.