Volt to Electron Volt Calculator

Enter a potential difference and a charge amount (in elementary charges or coulombs) to get the equivalent energy in electron-volts and joules using E = Q × V.

Quick Facts

Definition of 1 eV
1 eV = 1.602176634 × 10⁻¹⁹ J
The energy one elementary charge (an electron or proton) gains crossing a 1 V potential difference — this is the exact CODATA value of the elementary charge in coulombs.
Core formula
E (eV) = n × V
n is the charge in elementary-charge units; V is the potential difference in volts.
Joule form
E (J) = Q(C) × V(V)
Use this form when charge is measured directly in coulombs instead of as an electron count.
Common scales
1 keV = 10³ eV, 1 MeV = 10⁶ eV, 1 GeV = 10⁹ eV
Typical scales for X-rays (keV), nuclear reactions (MeV), and particle accelerators (GeV-TeV).

Your Results

Calculated
Energy (electron-volts)
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E = n × V, auto-scaled to keV/MeV/GeV
Energy (Joules)
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E = Q × V in SI units
Equivalent Elementary Charges
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Q ÷ e (1.602176634 × 10⁻¹⁹ C)
Charge Used
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Your charge input, converted to coulombs

Ready

Enter a voltage and a charge amount, then press Calculate.

Formula and Method for Converting Volts to Electron-Volts

A volt is a unit of electric potential difference — energy per unit charge (1 V = 1 J/C) — not a unit of energy by itself. An electron-volt (eV), on the other hand, is a unit of energy. To turn a voltage into an energy, you need to know how much charge moves through that potential difference: E = Q × V. When that charge is exactly one elementary charge (e = 1.602176634 × 10⁻¹⁹ C, the charge of a single electron or proton), the resulting energy in electron-volts is numerically identical to the voltage — which is precisely how the electron-volt is defined. This calculator generalizes that idea to any number of elementary charges, or to any charge given directly in coulombs.

How the conversion works

Enter the potential difference and its unit, then enter the charge that crosses it — either as a count of elementary charges (n, the default) or as a coulomb-based value. The calculator first converts both values into base SI units (volts and coulombs), then applies E (J) = Q × V to get the energy in joules. Dividing that result by the elementary charge (1.602176634 × 10⁻¹⁹ C) converts it to electron-volts; equivalently, when charge is entered as elementary-charge units, E (eV) = n × V directly. Large or small eV results are automatically shown in keV, MeV, GeV, or TeV so the number stays readable.

Common mistakes

  • Treating volts and electron-volts as the same kind of quantity: a "12 V" battery and "12 eV" of energy are not interchangeable — the eV figure only equals the voltage when exactly one elementary charge is involved.
  • Forgetting multiply-charged particles: an alpha particle or a doubly ionized atom carries charge 2e, not e, so it gains twice the energy (in eV) of a single electron crossing the same voltage — set the charge amount to 2 (not 1) for those cases.
  • Mixing charge units: entering "1" while the charge unit is set to coulombs means 1 whole coulomb (about 6.24 × 10¹⁸ elementary charges), not one electron — double-check the charge unit selector before reading the result.

Real-world uses of electron-volts

  • Photon and photoelectric-effect energies (visible light ≈ 1.6-3.2 eV) are almost always reported in eV rather than joules because joule values would be inconveniently tiny.
  • X-ray tube ratings in kilovolts directly set the maximum X-ray photon energy in keV, since each electron is accelerated through that voltage before striking the target.
  • Semiconductor band gaps (e.g., silicon ≈ 1.12 eV, gallium nitride ≈ 3.4 eV) are quoted in eV because they equal the energy an electron gains crossing that characteristic internal potential.
  • Particle accelerators describe beam energy in MeV, GeV, or TeV — the Large Hadron Collider accelerates protons (charge +e) through enormous effective potentials to reach about 6.5 TeV per proton.

Frequently Asked Questions

What is an electron-volt and how does it relate to volts?
An electron-volt (eV) is a unit of energy, not a unit of electric potential. It is defined as the kinetic energy gained by a single elementary charge (such as an electron or proton) when it accelerates through a potential difference of exactly 1 volt: 1 eV = 1.602176634 × 10⁻¹⁹ joules. A volt (J/C) only becomes an energy once you know how much charge crosses it.
How do I convert volts to electron-volts?
Multiply the potential difference (in volts) by the number of elementary charges that move through it: E (eV) = n × V. For a single electron or proton, n = 1, so the energy in eV is numerically equal to the voltage. For charge measured in coulombs, use E (eV) = Q(C) × V(V) ÷ 1.602176634 × 10⁻¹⁹.
Why isn't there a fixed volts-to-electron-volts conversion factor like inches to centimeters?
Volts measure potential difference (energy per unit charge), while electron-volts measure energy itself. Because energy equals charge times voltage (E = QV), you always need to know how much charge is moving before you can turn a voltage into an energy value — that is why this calculator asks for both a voltage and a charge amount.
What are typical electron-volt energies in physics?
Visible-light photons carry roughly 1.6-3.2 eV, X-ray tubes running at 20-150 kV produce X-ray photons up to 20-150 keV, nuclear decay energies are typically in the keV-to-MeV range, and particle accelerators like the LHC reach about 6.5 TeV per proton.

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