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Electronvolts to Joules Converter
↔ Convert J to eV instead

Common Conversions

eV J
0.001 1.602e-22
0.01 1.602e-21
0.026 4.142e-21
0.1 1.602e-20
1 1.602e-19
2 3.204e-19
5 8.011e-19
10 1.602e-18
13.6 2.179e-18
100 1.602e-17
1000 1.602e-16

Why this conversion matters in chemistry

The electronvolt is what atomic and molecular energies are naturally sized in. Ionization energies run a few eV to a few tens of eV, bond energies a few eV per bond, visible photons roughly 1.8 to 3.1 eV. That's a convenient range of numbers, which is exactly why spectroscopy uses it. But any calculation that ties back to thermodynamics needs joules, so you multiply by 1.602 × 10⁻¹⁹. That factor is the elementary charge — 1 eV is by definition the energy one electron picks up falling through a 1 V potential, so the conversion factor is just e in coulombs. Hydrogen's ionization energy of 13.6 eV works out to 2.18 × 10⁻¹⁸ J, which on its own is a number that tells you nothing; in eV it's one of the most memorable figures in all of physical chemistry.

Formula

J = eV × 1.60218 × 10⁻¹⁹

Worked Examples

13.6 eV = 2.179 × 10⁻¹⁸ J

The ionization energy of hydrogen. The Rydberg — arguably the most iconic number in all of atomic chemistry.

1 eV = 1.602 × 10⁻¹⁹ J

The defining conversion. An electron falling through a 1 V potential picks up exactly this much kinetic energy.

3.4 eV = 5.447 × 10⁻¹⁹ J

The band gap of gallium nitride — a wide-bandgap semiconductor used for UV and near-UV emitters. A number worth knowing once optoelectronics enters a conversation.

0.026 eV = 4.142 × 10⁻²¹ J

Thermal energy at room temperature (kT at 298 K). The rough floor below which any barrier becomes invisible to the molecules.

Frequently Asked Questions

How do I convert eV to joules?
Multiply by 1.60218 × 10⁻¹⁹. So 13.6 eV (hydrogen's ionization energy) works out to 2.18 × 10⁻¹⁸ J. The factor is the elementary charge in coulombs — that's not a coincidence, it's literally how the electronvolt is defined.
Why use eV at all?
Because atomic and molecular energies land in a nice range in it. Ionization energies are 1 to 25 eV, bond energies 1 to 10 eV per bond, visible photons around 2 eV — all numbers a chemist can hold in their head. The same values in joules become 10⁻¹⁹ numbers that communicate nothing about their relative sizes at a glance.
How do I convert eV to kJ/mol?
Multiply by 96.485. That factor is Faraday's constant divided by 1000 — so eV per particle times Avogadro divided by 1000 gives you kJ per mole. A 5 eV bond energy, for example, corresponds to 482 kJ/mol, which immediately puts it in the same range as the C–H bond values you'd see in a textbook.
What's kT in eV at room temperature?
About 0.026 eV at 298 K — sometimes quoted as 1/40 eV, which is close enough for mental arithmetic. It's the energy scale for thermal collisions. A barrier ten times larger than kT (0.26 eV) is getting hard to thermally cross; a hundred times larger (2.6 eV) is effectively frozen out. Useful mental calibration for thinking about reaction rates.