Volts to Electron-Volts Calculator

About the Volts to Electron-Volts Calculator

The electron-volt (eV) is the energy gained by a single electron accelerated through a potential difference of one volt: 1 eV = 1.602 × 10⁻¹⁹ joules. Despite its name, the electron-volt is a unit of energy — not voltage — and is the preferred unit in atomic, nuclear, and particle physics because energies at these scales are conveniently expressed in eV rather than tiny fractions of a joule.

The electron-volt connects voltage, energy, temperature, and photon wavelength through fundamental constants. An energy of 1 eV corresponds to a temperature of about 11,600 K, a photon wavelength of 1240 nm (near infrared), and the kinetic energy of an electron at rest accelerated through 1 volt. These conversions are used daily in spectroscopy, semiconductor physics, medical imaging, and high-energy physics.

This calculator converts between 10 energy units (eV, keV, MeV, GeV, TeV, meV, J, kJ, cal, erg), computes equivalent temperature and photon properties, calculates voltage-to-energy for charged particles, and shows relativistic speeds for five common particles at any given energy.

When This Page Helps

Converting between electron-volts and other energy units requires memorizing several fundamental constants, and the same energy may need to be expressed in temperature, wavelength, or particle-physics terms. This calculator is useful when you are comparing photon energies, checking semiconductor band gaps, or converting accelerator energies into a more practical unit.

How to Use the Inputs

1. Enter an energy value in the input field.
2. Select the energy unit (eV, keV, MeV, J, etc.) from the dropdown.
3. Read the converted values: eV, joules, temperature, photon frequency, and wavelength.
4. Use presets for common physics scenarios (visible light, X-ray, LHC, thermal).
5. To convert accelerating voltage to energy, enter voltage and charge multiple in the bottom section.
6. Check the particle table to see what speed each particle would have at the specified energy.

Example Calculation

Tips & Best Practices

• The shortcut λ(nm) = 1240 / E(eV) is extremely useful for quick photon wavelength calculations.
• Room temperature corresponds to about 25 meV (kT at 300 K) — electrons in a semiconductor have thermal energies of this order.
• In mass-energy equivalence (E = mc²), the electron rest mass is 0.511 MeV/c² and the proton is 938.3 MeV/c².
• Medical X-rays use 20-150 keV photons; CT scans use 80-140 keV; gamma rays in PET scans are 511 keV (from electron-positron annihilation).
• The LHC accelerates protons to 6.8 TeV — that is 6.8 × 10¹² eV per proton, giving γ ≈ 7,250 (nearly the speed of light).
• Chemical bond energies are 1-10 eV; nuclear binding energies are 1-10 MeV per nucleon.

The Electron-Volt in Spectroscopy

Atomic and molecular spectroscopy directly measures energy level differences in electron-volts. The hydrogen atom's ground-state ionization energy is 13.6 eV. Visible photon energies range from 1.65 eV (red, 750 nm) to 3.1 eV (violet, 400 nm). X-ray emission lines from inner-shell electron transitions have energies of keV, and nuclear gamma rays reach MeV. The electron-volt provides a natural scale for all these phenomena.

Semiconductor Band Gaps

In semiconductor physics, the band gap energy (in eV) determines a material's electronic and optical properties. Silicon's indirect band gap is 1.12 eV (infrared), gallium arsenide's direct gap is 1.42 eV (near IR), and gallium nitride's gap is 3.4 eV (UV). LEDs and laser diodes emit photons with energy approximately equal to the band gap, making eV the natural unit for optoelectronic device design.

Particle Accelerators and High-Energy Physics

Particle accelerators are characterized by the energy they impart to particles, measured in eV. Medical linacs operate at 6-20 MeV, synchrotron light sources at hundreds of MeV to several GeV, and the Large Hadron Collider (LHC) at 6.8 TeV per beam. At these energies, particles travel at 99.9999991% the speed of light, and the distinction between kinetic energy and rest mass energy becomes essential.

Frequently Asked Questions

• Is an electron-volt a unit of voltage or energy?

  Energy. Despite the name, 1 eV is the amount of kinetic energy gained by a single electron (charge e = 1.602×10⁻¹⁹ C) when accelerated through a potential difference of 1 volt. In SI: 1 eV = 1.602×10⁻¹⁹ joules.

• Why do physicists use eV instead of joules?

  Because particle-scale energies are inconveniently small in joules. A photon of visible light has about 2 eV (= 3.2×10⁻¹⁹ J). Working in eV eliminates the need for 10⁻¹⁹ factors and makes orders of magnitude intuitive: keV for X-rays, MeV for nuclear, GeV for particle physics.

• How do I convert eV to temperature?

  Divide by Boltzmann's constant: T = E / k_B. In convenient units: 1 eV ≈ 11,604 K. This is useful in plasma physics and semiconductor physics where thermal energy kT determines carrier behavior.

• What is mass-energy equivalence in eV?

  Einstein's E = mc² means mass can be expressed in energy units. The electron has a rest mass energy of 0.511 MeV (= 8.2×10⁻¹⁴ J). Particle physicists express mass in MeV/c² or GeV/c² as standard practice.

• What does the relativistic speed calculation assume?

  It assumes the input energy is the particle's kinetic energy (not total energy). The Lorentz factor is γ = 1 + KE/(mc²), and the speed is β = v/c = √(1 − 1/γ²). For electrons at keV energies, this gives significantly relativistic speeds; protons need MeV energies to become relativistic.

• Why is 1240 eV·nm a useful number?

  The product hc = 6.626×10⁻³⁴ × 2.998×10⁸ = 1.240×10⁻⁶ eV·m = 1240 eV·nm. This means λ(nm) = 1240 / E(eV) — a quick photon wavelength shortcut. For example, 2 eV → 620 nm (red), 3 eV → 413 nm (violet).