Volt to Electron Volt Calculator

Background.

A volt is not a unit of energy, yet accelerator physicists happily say a proton “has 2 MeV after a 2 MV gap”. The bridge is the elementary charge: the electron volt is defined as the energy one elementary charge gains falling through one volt of potential difference. Because the charge and the volt pair off so cleanly, the numerical rule is simply E in eV = z × V, where z is how many elementary charges the particle carries.

That rule is what this calculator evaluates. An electron or proton (z = 1) crossing a 120 V gap gains 120 eV; an alpha particle (z = 2) crossing the same gap gains 240 eV, because the same field does twice the work on twice the charge. The dependence on z is the part intuition most often drops — voltage alone never fixes the energy.

The eV earns its keep as the natural currency of atomic and particle physics: chemical bonds run a few eV, visible photons 1.6–3.3 eV, X-ray tubes tens of keV, medical linacs a few MeV, and the LHC 6.8 TeV per proton. Quoting these in joules would bury the physics under nineteen zeros — one eV is exactly 1.602 176 634×10⁻¹⁹ J, a conversion made exact when the 2019 SI redefinition fixed the elementary charge.

The calculator reports magnitude only. Whether the particle gains or loses that energy depends on the sign of its charge and which way it crosses the gap — an electron accelerated toward a positive plate gains 120 eV of kinetic energy; the same electron pushed the other way costs exactly that much work.

What is volt to electron volt calculator?

The electron volt (symbol eV) is the kinetic energy an elementary charge e acquires when accelerated through a potential difference of one volt: 1 eV = 1.602 176 634×10⁻¹⁹ joules, exactly, since the 2019 SI fixed the value of e. It is a unit of energy — not voltage — sized for the atomic world. “Converting volts to electron volts” therefore always smuggles in a charge: the computation is E = qV, and it is only because q is measured in elementary charges that the numbers look like a unit swap.

How to use this calculator.

1. 01Enter the potential difference in volts that the particle actually traverses — for a multi-stage accelerator, the sum of the stage voltages it crosses.
2. 02Enter the charge number z: 1 for electrons and protons, 2 for alpha particles and Ca²⁺, 3 for Al³⁺, and so on.
3. 03Read the energy in eV; divide by 1,000 or 1,000,000 mentally for keV or MeV when the voltage is large.
4. 04Multiply by 1.602×10⁻¹⁹ if a formula downstream needs joules — kinetic-energy comparisons with ½mv², for instance.
5. 05Keep track of sign separately: the calculator reports the magnitude of the energy change, and whether that is a gain or a cost depends on the charge's sign and the direction of travel.

The formula.

Work done on a charge q by an electric potential difference V is W = qV — the defining property of the volt as a joule per coulomb. Write the charge as z elementary charges, q = z·e, and the work becomes W = z·e·V joules. The electron volt is defined as e joules-per-volt of exactly this kind, so dividing W by e leaves the strikingly simple numeric rule E(eV) = z×V: the unit conversion and the charge magnitude cancel. Nothing about the particle's mass enters — a proton and an electron crossing the same 120 V gap gain the same 120 eV, though the lighter electron ends up moving roughly 43 times faster since v = √(2E/m). The engine multiplies the two inputs with Decimal arithmetic and rounds once to twelve significant digits.

A worked example.

Frequently asked questions.

References& sources.

1. [1]BIPM, SI Brochure, 9th ed., table of non-SI units accepted for use with SI.
2. [2]NIST, Guide for the Use of the International System of Units, SP 811.
3. [3]BIPM, The International System of Units (SI Brochure), 9th ed., version 3.01, coherent derived units and quantity equations.