About the eV to Joules Converter
The electronvolt is the energy an electron gains when it moves through one volt, and it is the natural unit for atoms, photons and particle physics. Joules are the SI unit. This converter turns electronvolts into joules using the exact value fixed in 2019: one electronvolt is 1.602176634 × 10^-19 joules. Type any number of eV, including keV, MeV or GeV values written out, and read the joules at once. The extra rows show the same energy in kilojoules, calories, watt-hours and more. It is meant for physics and chemistry homework, spectroscopy, semiconductor band gaps and radiation questions, and it works in your browser without sending anything.
Updated October 2026
How to use the eV to Joules Converter
- 1Type the energy in electronvolts.
- 2Read the joules at the top, shown in scientific notation for small values.
- 3See other units in the rows below.
- 4Press Copy to copy the sentence.
- 5Try another value, for example 13.6 eV for hydrogen.
The formula
joules = eV × 1.602176634 × 10^-19. The factor is the elementary charge in coulombs, because one electronvolt is one elementary charge times one volt.
For the reverse, divide joules by the same number with the Joules to eV converter.
Useful reference values
- Hydrogen ionisation energy: 13.6 eV
- Visible photon: about 2 to 3 eV
- Silicon band gap: about 1.12 eV
- X-ray photon: about 1 to 100 keV
- Large Hadron Collider proton beam: about 6.8 TeV per proton in 2022
Why physicists use eV
Writing 2.18 × 10^-18 J for an atomic energy is awkward, while 13.6 eV is easy to read. The unit also links energy to voltage: an electron accelerated through 5 V gains 5 eV.
Temperature can be expressed in eV too, since 1 eV corresponds to about 11,604 kelvin.
Worked examples
Hydrogen's ground state needs 13.6 eV to ionise, which is 13.6 × 1.602176634 × 10^-19 = 2.178 × 10^-18 J. A photon of 2.5 eV, such as blue-green light, carries 4.005 × 10^-19 J. A 1 MeV gamma ray carries 1.602 × 10^-13 J, still far less than a joule.
To check a result, remember that 1 eV is roughly 1.6 × 10^-19 J. If your answer is within a factor of ten of the number of eV times 1.6 × 10^-19, the order of magnitude is right.
eV, keV, MeV and GeV
Prefixes work as usual: 1 keV is 1,000 eV, 1 MeV is a million, 1 GeV a billion and 1 TeV a trillion. Type the full number of eV, for example 5e6 for 5 MeV, to convert any of them here.
Phone and computer
Results update as you type, and tiny values are written as powers of ten so they stay readable. Electronvolts are handy for atoms and light, while joules suit larger energy sums. Convert back with the Joules to eV Converter, use the eV to Volts Calculator for charge questions, and find the light's wavelength with the Wavelength Calculator.
Features
- Exact 2019 elementary charge, 1.602176634 × 10^-19 C
- Scientific notation for tiny results
- Ten significant digits
- Kilojoules, calories, watt-hours and more shown together
- Copy button
- Runs in your browser
Frequently asked questions
How many joules are in one electronvolt?
Exactly 1.602176634 × 10^-19 joules, since the 2019 redefinition of the SI units.
How do I convert eV to joules by hand?
Multiply by 1.602176634 × 10^-19. For example 13.6 eV, the ionisation energy of hydrogen, is about 2.1787 × 10^-18 J.
How do I convert keV, MeV and GeV?
Multiply by 1,000, 1,000,000 or 1,000,000,000 first. For example 1 MeV is 10^6 eV, which is 1.602176634 × 10^-13 J.
Why is the number so small?
An electron is tiny and one volt is a small step. A joule is a human-sized amount of energy, so everyday atomic energies are a tiny fraction of it.
What is a photon of visible light in eV?
Visible light photons carry roughly 1.8 to 3.1 eV, which is about 2.9 × 10^-19 to 5.0 × 10^-19 J.
Is the value exact?
Yes. The elementary charge has been an exact number since 2019, so the conversion is exact.
Does the tool send my number anywhere?
No.