Electron Volt to Joules Converter

Converting electron volts (eV) to joules (J) is essential in atomic physics, quantum mechanics, and particle science. An electron volt represents the energy gained by a single electron when accelerated through an electric potential difference of one volt. The joule, meanwhile, is the SI unit of energy used across all scientific disciplines.

Energy Converter

eV to Joules Conversion Table

This table shows common electron volt values and their equivalent energy in joules. The values range from single electron volts to giga-electron volts, covering typical applications in atomic and nuclear physics.

Electron Volts (eV) Joules (J) Scientific Notation
1 eV 0.0000000000000000001602 J 1.602 × 10-19 J
10 eV 0.000000000000000001602 J 1.602 × 10-18 J
100 eV 0.00000000000000001602 J 1.602 × 10-17 J
1 keV (1,000 eV) 0.0000000000000001602 J 1.602 × 10-16 J
10 keV 0.000000000000001602 J 1.602 × 10-15 J
100 keV 0.00000000000001602 J 1.602 × 10-14 J
1 MeV (1,000,000 eV) 0.0000000000001602 J 1.602 × 10-13 J
10 MeV 0.000000000001602 J 1.602 × 10-12 J
100 MeV 0.00000000001602 J 1.602 × 10-11 J
1 GeV (1,000,000,000 eV) 0.0000000001602 J 1.602 × 10-10 J
10 GeV 0.000000001602 J 1.602 × 10-9 J
100 GeV 0.00000001602 J 1.602 × 10-8 J

Conversion Formula

The conversion between electron volts and joules uses this precise relationship:

E (J) = E (eV) × 1.602176634 × 10-19

Where E represents energy. This conversion factor is defined by the elementary charge of an electron.

Step-by-Step Conversion Process

Converting electron volts to joules requires multiplying by the elementary charge constant. Here’s how it works:

  • Identify the energy value in electron volts
  • Multiply by 1.602176634 × 10-19
  • The result gives you energy in joules
  • For reverse conversion (J to eV), divide joules by the same constant

Worked Example

Question: Convert 5.5 MeV to joules

Solution:

First, convert MeV to eV: 5.5 MeV = 5,500,000 eV

Then multiply by the conversion factor:

5,500,000 × 1.602176634 × 10-19 = 8.812 × 10-13 J

Answer: 5.5 MeV = 8.812 × 10-13 joules

What Are Electron Volts?

The electron volt is a unit of energy particularly suited for atomic and subatomic scales. When a single electron moves through an electric potential difference of one volt, it gains exactly one electron volt of kinetic energy. This makes eV incredibly practical for describing energies in particle physics, where dealing with joules would require awkward scientific notation.

Physicists often use multiples of electron volts:

  • keV (kilo-electron volt) = 1,000 eV – typical for X-ray energies
  • MeV (mega-electron volt) = 1,000,000 eV – used in nuclear physics
  • GeV (giga-electron volt) = 1,000,000,000 eV – particle accelerator energies
  • TeV (tera-electron volt) = 1,000,000,000,000 eV – Large Hadron Collider range

When Do You Need This Conversion?

Converting between eV and joules becomes necessary when working across different areas of physics. Atomic physicists naturally speak in electron volts, whilst engineers and chemists typically work in joules. Here are situations where you’ll need this conversion:

  • Calculating energy requirements for ionisation processes
  • Analysing particle collision data from accelerators
  • Determining photon energies in spectroscopy
  • Converting between quantum mechanics equations and classical energy expressions
  • Working with semiconductor band gap energies
  • Studying radioactive decay energies

Energy Units Conversions

Beyond the eV-joule relationship, energy appears in various units across different fields. This table helps you navigate between them.

From To Multiply By
eV Joules (J) 1.602 × 10-19
eV Kilowatt-hours (kWh) 4.45 × 10-26
eV Calories (cal) 3.83 × 10-20
Joules (J) eV 6.242 × 1018
Joules (J) Kilojoules (kJ) 0.001
Joules (J) Watt-seconds (Ws) 1
keV Joules (J) 1.602 × 10-16
MeV Joules (J) 1.602 × 10-13
GeV Joules (J) 1.602 × 10-10

Everyday Context

Electron volts measure extraordinarily small energies by everyday standards. To put this in perspective, a 1.5-volt AA battery moving a single electron provides 1.5 eV of energy. Meanwhile, a flying mosquito carries roughly 1 trillion eV (1 TeV) of kinetic energy – the same energy scale that particle physicists achieve with individual protons in the Large Hadron Collider.

A single photon of visible light carries between 1.6 and 3.4 eV, depending on its colour. Red light sits at the lower end whilst violet occupies the higher energies. This relationship explains why ultraviolet light (higher eV) causes sunburn whilst infrared (lower eV) simply warms your skin.

Note about scientific notation: When working with electron volt conversions, you’ll frequently encounter scientific notation (powers of 10). This is essential because the numbers involved span enormous ranges – from individual atoms to cosmic rays carrying 1020 eV.

FAQs

How many joules equal one electron volt?

One electron volt equals exactly 1.602176634 × 10-19 joules. This value is defined by the elementary charge of an electron and represents an extremely small amount of energy on the macroscopic scale.

Why do physicists use eV instead of joules?

Electron volts provide more convenient numbers when describing atomic-scale phenomena. Writing “13.6 eV” for hydrogen’s ionisation energy is simpler than “2.18 × 10-18 J”. The eV naturally fits the energy scales encountered in quantum mechanics and particle physics.

What’s the difference between eV and J in practical terms?

Joules measure energy at any scale and serve as the SI standard unit. Electron volts specifically suit atomic and subatomic physics. You’d measure a light bulb’s energy consumption in joules, but describe an X-ray photon’s energy in keV.

Can I convert other units to eV?

Yes. Any energy unit converts to eV by first converting to joules, then multiplying by 6.242 × 1018 eV/J. For instance, 1 calorie = 4.184 J = 2.611 × 1019 eV.

What energy range do different eV multiples cover?

eV suits atomic physics and chemistry (bond energies, ionisation). keV works for inner-shell electrons and X-rays. MeV describes nuclear reactions and gamma rays. GeV and TeV appear in particle accelerators and cosmic ray physics.

Is the eV to J conversion exact?

Yes. Since 2019, the elementary charge (and therefore the eV) has an exact defined value of 1.602176634 × 10-19 coulombs. This makes the conversion between eV and joules exact by definition.

How do you convert joules back to eV?

Divide the energy in joules by 1.602176634 × 10-19, or equivalently, multiply by 6.242 × 1018. For example, 1 J = 6.242 × 1018 eV.

References

  • National Institute of Standards and Technology (NIST). (2022). CODATA Recommended Values of the Fundamental Physical Constants: 2018. Available at: https://physics.nist.gov/cuu/Constants/ [Accessed 30 December 2025].
  • Bureau International des Poids et Mesures (BIPM). (2019). The International System of Units (SI), 9th edition. Sèvres: BIPM. ISBN 978-92-822-2272-0.
  • Mohr, P.J., Newell, D.B. and Taylor, B.N. (2016). CODATA recommended values of the fundamental physical constants: 2014. Reviews of Modern Physics, 88(3), 035009. doi:10.1103/RevModPhys.88.035009.
  • Griffiths, D.J. (2017). Introduction to Quantum Mechanics, 3rd edition. Cambridge: Cambridge University Press. ISBN 978-1107189638.

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