Volts to eV Converter
Convert volts to electronvolts with the particle's charge state: E(eV) = V × z. Reverse eV → volts, plus exact joules.
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eV
Energy in joules—
Charge state used—
Enter a voltage and press Convert.
1 eV = 1.602176634×10⁻¹⁹ J exactly (SI 2019). An electronvolt is energy, not voltage — it is the energy one elementary charge gains falling through 1 V.
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volts
Energy in joules—
Enter an energy and press Convert.
Physics examples
Real-world cases computed from E = V × z (z shown per case).
| Case | Volts | z | Energy | Joules |
|---|---|---|---|---|
| Thermal energy at room temp (kT) 298 K (~25 °C), single electron | 0.025693 | 1 | 0.025693 eV | 4.116e-21 J |
| AA battery across electron 1.5 V, z = 1 | 1.5 | 1 | 1.5 eV | 2.403e-19 J |
| Mains 230 V electron z = 1 | 230 | 1 | 230 eV | 3.685e-17 J |
| Rydberg (H ionization) z = 1 | 13.6 | 1 | 13.6 eV | 2.179e-18 J |
| XPS Al K-alpha z = 1 | 1,486.6 | 1 | 1.4866 keV | 2.382e-16 J |
| SEM electron beam 10 kV, z = 1 | 10,000 | 1 | 10 keV | 1.602e-15 J |
| Electron rest mass 511 keV, z = 1 | 511,000 | 1 | 511 keV | 8.187e-14 J |
| Fe²⁶⁺ ion at 50 V z = 26 | 50 | 26 | 1.3 keV | 2.083e-16 J |
Which tool should you use? The sister tool volts-to-joules-calculator works at the macroscopic scale — batteries (E = V × Q) and capacitors (E = ½CV²) — and gives joules directly. This tool works at the single-particle scale: it converts volts to electronvolts using the particle's charge state z, then also shows joules. Different scale, different physics.
Related calculators:
- volts-to-joules-calculator — macroscopic E = V·I·t, battery mAh, capacitor ½CV²
- volts-to-ohms — Ohm's law V = I·R, voltage dividers
- voltage-converter — V, mV, µV, kV, MV unit hub
Frequently asked questions
What is the formula to convert volts to eV?
E (in electronvolts) = V (in volts) × z, where z is the charge state — the particle's charge in units of the elementary charge. For example, an electron (z = 1) accelerated across 10 V gains 10 eV of kinetic energy: 10 V × 1 = 10 eV.
What is z, the charge state?
z counts how many elementary charges the particle carries: z = 1 for a single electron or proton, z = 2 for He²⁺ (alpha particle), z = 13 for Al¹³⁺, z = 26 for Fe²⁶⁺, and z = 82 for Pb⁸²⁺. The calculator defaults to z = 1.
How many eV is 1 volt for an electron?
Exactly 1 eV for z = 1. That is the definition of the electronvolt: the kinetic energy gained by one elementary charge falling through a 1-volt potential difference, equal to 1.602e-19 J.
How many joules is 1 eV?
Exactly 1.602176634×10⁻¹⁹ J. This is an exact SI definition (2019 redefinition). So 13.6 eV (the hydrogen ionization energy) equals 2.179e-18 J.
How do I convert eV back to volts?
Divide by the charge state: V = E ÷ z. For example, 1486.6 eV with z = 1 converts back to 1486.6 V. Use the reverse (eV → V) tab above.
Is an electronvolt a unit of voltage?
No — the electronvolt (eV) is a unit of energy, not voltage. The volt measures electric potential per unit charge (energy divided by charge). Confusing the two is the most common mistake: 1 eV is a tiny amount of energy (1.602e-19 J), while 1 V is a potential that can give that energy to one electron.
What is the charge state z for Al¹³⁺?
z = 13, because the ion carries 13 elementary charges. So 1 V × 13 = 13 eV, which equals 2.083e-18 J.
What is the difference from a volts-to-joules calculator?
The sister tool volts-to-joules-calculator works at the macroscopic scale: batteries (E = V × Q) and capacitors (E = ½CV²), giving joules directly. This tool works at the single-particle scale: it converts volts to electronvolts using the particle's charge state z, then also shows joules.
What energy does a 10 kV SEM electron beam have?
10,000 V × 1 = 10,000 eV, shown as 10 keV. A typical scanning electron microscope runs 1–30 kV, so electrons carry 1–30 keV each.
What is the electron rest-mass energy in eV and joules?
511 keV, i.e. 511,000 eV. In joules that is 8.187e-14 J — computed as 511,000 × 1.602176634×10⁻¹⁹ J.
What happens with negative volts?
The sign is preserved: −5 V with z = 1 gives −5 eV. Physically the sign indicates direction (deceleration), and the kinetic-energy magnitude is what usually matters.
How much is room-temperature thermal energy in eV?
kT at 298 K is about 0.025693 eV (25.693 meV) for a single particle — one reason eV is the natural unit in solid-state physics and plasma diagnostics.
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