About the Joules to eV Converter
When an energy is given in joules but you work with atoms, photons or particles, you need electronvolts. This converter divides joules by the exact elementary charge, 1.602176634 × 10^-19, which is how many joules one electronvolt is. One joule is therefore about 6.241509 × 10^18 eV. Type the joules, including very small numbers such as 3.2 × 10^-19, and read the electronvolts at once, together with the same energy in keV, MeV and GeV in the rows below. It works in your browser, and the numbers stay on your device. Use it for physics homework, photon energy questions, radiation and semiconductor problems.
Updated October 2026
How to use the Joules to eV Converter
- 1Type the energy in joules. Scientific notation such as 3.2e-19 is accepted.
- 2Read the electronvolts at the top of the result.
- 3Look at the other rows for the same energy in more units.
- 4Press Copy to copy the sentence.
- 5Change the number to try another value.
The formula
eV = joules ÷ 1.602176634 × 10^-19. The same factor is used in the eV to Joules converter, so each page undoes the other.
A handy shortcut: 1 J is about 6.24 × 10^18 eV.
Examples
- 1.602176634 × 10^-19 J = 1 eV
- 1 × 10^-18 J is about 6.24 eV
- 1 × 10^-13 J is about 624 keV
- 1 J is about 6.24 × 10^18 eV
When to use eV
Photons, atomic transitions, band gaps and particle masses all come in electronvolts. A mass of 0.511 MeV for the electron means its rest energy is about 8.19 × 10^-14 J. Moving between joules and eV lets you check a calculation done in SI units against tables printed in eV.
If you only know a voltage and a charge, the Volts to Joules calculator may be quicker.
Photon energy example
A laser pointer at 650 nm emits photons of energy hc divided by the wavelength, which is about 3.06 × 10^-19 J. Enter that here and you get about 1.91 eV. The same number written in joules would be hard to compare with the 1.1 eV band gap of silicon, while in eV the comparison is immediate.
Because the electronvolt links energy to voltage, the answer also tells you the voltage an electron would need to fall through to gain that energy.
Large and small results
Everyday energies in joules come out as enormous numbers of eV, so the result is shown in powers of ten. Typing 1 gives about 6.241509074 × 10^18, which is the number of electrons that carry one joule when moved through one volt.
Phone and computer
The calculator updates as you type and shows tiny and huge values in scientific notation. Joules suit everyday sums, and electronvolts fit atoms. Reverse the answer with the eV to Joules Converter, convert the voltage side with the Volts to eV Calculator, and find the light's wavelength with the Wavelength Calculator.
Features
- Exact 2019 elementary charge
- Accepts scientific notation like 3.2e-19
- Large results in powers of ten
- Ten significant digits
- Copy button
- Private, works offline
Frequently asked questions
How many electronvolts are in a joule?
About 6.241509074 × 10^18 eV, which is 1 divided by 1.602176634 × 10^-19.
How do I convert joules to eV by hand?
Divide the joules by 1.602176634 × 10^-19. For example 3.2 × 10^-19 J is about 2.0 eV.
How do I get keV, MeV or GeV?
Divide the eV result by 1,000, 1,000,000 or 1,000,000,000.
Can I type very small numbers?
Yes. Write 3.2e-19 for 3.2 × 10^-19. The result is shown in powers of ten.
What is the energy of a photon in eV?
Use E = hf or E = hc divided by the wavelength. A green photon of 532 nm has about 3.73 × 10^-19 J, which is about 2.33 eV.
Is the conversion exact?
Yes, because the elementary charge has been an exact number since 2019.
Is anything uploaded?
No.