Electron-volts to Joules (eV to J)
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Electronvolts-to-joules conversions translate atomic-and-molecular-physics, particle-physics, semiconductor-engineering, and chemistry electronvolt-scale energy figures into the SI joule primary used for macroscopic-scale physics-and-engineering reference. A 1 eV semiconductor-band-gap electron-energy translates to 1.602 × 10⁻¹⁹ J on the SI engineering reference; a 13.6 eV hydrogen-ionisation-energy translates to 2.18 × 10⁻¹⁸ J; a 1 GeV particle-physics beam-energy translates to 1.602 × 10⁻¹⁰ J. The factor is exact at 1 eV = 1.602176634 × 10⁻¹⁹ J via the 2019 SI redefinition that fixed the elementary charge at exactly 1.602176634 × 10⁻¹⁹ C.
How to convert Electron-volts to Joules
Formula
J = eV × 1.602176634 × 10⁻¹⁹
To convert electronvolts to joules, multiply the eV figure by 1.602176634 × 10⁻¹⁹ — exactly. The factor is fixed by the 2019 SI redefinition that set the elementary charge e = 1.602176634 × 10⁻¹⁹ C exactly, with one eV defined as the kinetic energy gained by an electron accelerated through a potential difference of one volt (1 eV = e × 1 V = 1.602176634 × 10⁻¹⁹ J). For mental math, treat the factor as 1.6 × 10⁻¹⁹ for everyday physics work — the approximation is within 0.13% of exact. The conversion runs at every atomic-and-molecular-and-particle-and-semiconductor physics-eV source to SI-engineering-J destination boundary, with the factor exact rather than measured and the conversion adding no rounding error of its own.
Worked examples
Example 1 — 1 eV
One electronvolt equals exactly 1.602176634 × 10⁻¹⁹ joules, derived from the elementary charge e = 1.602176634 × 10⁻¹⁹ C exactly via the 2019 SI redefinition. The factor is fixed by definition rather than measured.
Example 2 — 1.12 eV
One point one two electronvolts — the silicon-semiconductor band-gap energy — converts to 1.795 × 10⁻¹⁹ J on the SI device-engineering documentation. The eV-figure is the semiconductor-physics primary; the J-figure is the SI device-engineering reference.
Example 3 — 13.6 eV
Thirteen point six electronvolts — the hydrogen-atom Lyman-alpha ionisation-energy — converts to 2.18 × 10⁻¹⁸ J on the SI chemistry-engineering documentation. The eV-figure is the atomic-physics primary; the J-figure is the SI chemistry-engineering reference.
eV to J conversion table
| eV | J |
|---|---|
| 1 eV | 0 J |
| 2 eV | 0 J |
| 3 eV | 0 J |
| 4 eV | 0 J |
| 5 eV | 0 J |
| 6 eV | 0 J |
| 7 eV | 0 J |
| 8 eV | 0 J |
| 9 eV | 0 J |
| 10 eV | 0 J |
| 15 eV | 0 J |
| 20 eV | 0 J |
| 25 eV | 0 J |
| 30 eV | 0 J |
| 40 eV | 0 J |
| 50 eV | 0 J |
| 75 eV | 0 J |
| 100 eV | 0 J |
| 150 eV | 0 J |
| 200 eV | 0 J |
| 250 eV | 0 J |
| 500 eV | 0 J |
| 750 eV | 0 J |
| 1000 eV | 0 J |
| 2500 eV | 0 J |
| 5000 eV | 0 J |
Common eV to J conversions
- 0.5 eV=0 J
- 1 eV=0 J
- 1.12 eV=0 J
- 1.42 eV=0 J
- 3.4 eV=0 J
- 5.14 eV=0 J
- 13.6 eV=0 J
- 1000 eV=0 J
- 1000000 eV=0 J
- 1000000000 eV=0 J
What is a Electron-volt?
The electron-volt (eV) is exactly 1.602176634 × 10⁻¹⁹ joules by the 2019 SI redefinition. One electron-volt is the kinetic energy gained by a single electron accelerated through a potential difference of one volt, so 1 eV = 1 e × 1 V = 1.602176634 × 10⁻¹⁹ C × 1 V = 1.602176634 × 10⁻¹⁹ J. The recognised symbol is "eV", with lowercase "e" for electron and uppercase "V" honouring Alessandro Volta. Higher-energy multiples use keV (1000 eV, atomic X-ray spectroscopy and electron-microscopy beam energies), MeV (10⁶ eV, nuclear-physics binding energies and medical radiology), GeV (10⁹ eV, high-energy particle-physics collisions), and TeV (10¹² eV, LHC-scale collision energies). The eV is not part of the SI but is recognised by NIST, BIPM and CODATA as a non-SI unit accepted for use with the SI in atomic, molecular, particle-physics and high-energy-physics contexts.
The electron-volt was introduced in early-twentieth-century atomic and particle physics as the natural energy unit at the atomic and subatomic scale, where typical interaction energies fall in the 1-1000 eV range for atomic-physics work and the GeV-to-TeV range for particle-physics work. The unit was formally adopted by the International Union of Pure and Applied Physics (IUPAP) in the 1930s and has persisted as the dominant energy unit in atomic, molecular and particle physics ever since. The 2019 SI redefinition fixed the elementary charge e at exactly 1.602176634 × 10⁻¹⁹ C, which transitively fixed the electron-volt at exactly 1.602176634 × 10⁻¹⁹ J — eliminating the historical measurement-precision uncertainty that had previously affected eV-to-J conversions. The eV is the natural energy scale for atomic-spectroscopy work (typical visible-light photon energies at 1.6-3.3 eV), chemical-bond energies (typical C-C bond at 3.6 eV per bond), semiconductor band-gaps (silicon at 1.12 eV, GaAs at 1.42 eV), and particle-physics interaction energies (LHC pp collisions at 13 TeV centre-of-mass energy).
Atomic and molecular physics: electron-volts are the natural energy unit for atomic-spectroscopy transitions, ionisation potentials and chemical-bond energies. Visible-light photon energies fall in the 1.6-3.3 eV range (red light at 1.77 eV, violet light at 3.26 eV); ionisation potentials of common atoms range 4-25 eV (caesium at 3.89 eV, hydrogen at 13.60 eV, helium at 24.59 eV); chemical-bond energies fall in the 1-10 eV per bond range. Semiconductor physics and electronics: semiconductor band-gaps are universally denominated in eV — silicon at 1.12 eV (the semiconductor-industry workhorse), GaAs at 1.42 eV, GaN at 3.4 eV, SiC at 3.26 eV. Solar-cell efficiency calculations work directly with band-gap eV figures. Nuclear physics: nuclear-binding energies and gamma-ray energies fall in the keV-to-MeV range. Cobalt-60 emits gamma rays at 1.17 and 1.33 MeV; medical-radiology X-ray tubes operate at 50-150 keV. Particle physics: high-energy-physics interaction energies run from GeV (Tevatron at 1.96 TeV centre-of-mass) to TeV (LHC at 13 TeV centre-of-mass) scale. Mass-energy equivalence: particle masses are routinely reported in MeV/c² or GeV/c² via E = mc² — the electron at 0.511 MeV/c², the proton at 938 MeV/c², the Higgs boson at 125 GeV/c².
What is a Joule?
The joule (J) is the SI derived unit of energy, work, and heat. One joule equals the work done by a force of one newton acting over a distance of one metre (1 J = 1 N·m), or equivalently the energy transferred when one watt of power acts for one second (1 J = 1 W·s). In electrical terms, one joule equals one coulomb of charge moved through a potential difference of one volt (1 J = 1 C·V). The joule is anchored to the SI base units kilogram, metre and second through the relationship 1 J = 1 kg·m²·s⁻². Since the 2019 SI redefinition the joule is fixed via the Planck constant h = 6.62607015 × 10⁻³⁴ J·s exactly, with the kilogram derived from this anchoring rather than the historical artifact-based definition. The joule is the universal SI energy unit and replaces older heat-and-energy units (calorie, BTU, erg, foot-pound) in modern technical work.
The joule is named after James Prescott Joule (1818-1889), the English physicist whose 1840s experiments on the mechanical equivalent of heat established that mechanical work and thermal energy are interconvertible quantities of the same physical type. Joule's most famous experiment used a falling weight to drive a paddle wheel in an insulated water tank, measuring the temperature rise per joule of mechanical work input — establishing the mechanical equivalent of heat at approximately 4.155 J per calorie (modern value 4.184 J per IT calorie). His paper "On the Mechanical Equivalent of Heat" presented to the British Association in 1843 was initially met with skepticism but became foundational to the first law of thermodynamics. The unit "joule" was formally adopted at the 2nd International Electrical Congress in 1889 (the year of Joule's death) and incorporated into the SI as the derived unit for energy at the 11th CGPM in 1960. The 2019 SI redefinition fixed the joule via the kilogram-Planck-constant chain through h = 6.62607015 × 10⁻³⁴ J·s exactly.
The joule appears across every modern scientific and engineering discipline. Physics and chemistry research universally denominate energy in joules (or kJ for chemical-bond energies and reaction enthalpies, MJ for combustion-energy figures). Mechanical engineering uses joules for kinetic-energy and work calculations: a 1500 kg car at 100 km/h has a kinetic energy of 579 kJ. Electrical engineering uses joules at the device level (Wh and kWh for billing and inventory but joule-second is the canonical unit-time relationship). Food science and nutrition labelling under EU Regulation 1169/2011 mandate kJ-and-kcal dual-display on every prepacked food sold in the EU, replacing the older kcal-only convention. Particle physics uses electron-volts (eV) for individual-particle energies but the underlying calculations preserve the joule via the 1.602176634 × 10⁻¹⁹ J/eV conversion factor. Thermodynamics, materials science, atmospheric chemistry, and combustion engineering all operate in joules through their underlying equations even when display values are rendered in legacy units.
Real-world uses for Electron-volts to Joules
Semiconductor band-gap eV translated to J for solid-state physics and device-engineering documentation
Semiconductor band-gap energies expressed in eV translate to J for solid-state physics, semiconductor-device-engineering, and ISO-and-EN scientific documentation. A 1.12 eV silicon band-gap translates to 1.795 × 10⁻¹⁹ J; a 3.4 eV gallium-nitride band-gap translates to 5.45 × 10⁻¹⁹ J; a 0.66 eV germanium band-gap translates to 1.06 × 10⁻¹⁹ J; a 1.42 eV gallium-arsenide band-gap translates to 2.27 × 10⁻¹⁹ J. The conversion runs at every semiconductor-physics-eV source to SI-J device-engineering documentation step.
Particle-physics beam-energy GeV-and-TeV translated to J for accelerator-physics-engineering documentation
Particle-physics-accelerator beam-energy specifications in GeV (10⁹ eV) and TeV (10¹² eV) translate to J for accelerator-physics-engineering, beam-power-and-luminosity calculations, and CERN-Fermilab-KEK-and-similar facility-documentation. A 7 TeV LHC proton-beam energy translates to 1.12 × 10⁻⁶ J per particle; a 3 TeV total-collision-energy translates to 4.81 × 10⁻⁷ J per collision; a 1 GeV typical-cyclotron-beam translates to 1.6 × 10⁻¹⁰ J per particle. The conversion runs at every particle-physics-eV source to accelerator-engineering-J documentation step.
Atomic-and-molecular spectroscopy eV translated to J for chemistry-engineering and JCAMP-DX format
Atomic-and-molecular spectroscopy transition energies expressed in eV translate to J for chemistry-engineering documentation, JCAMP-DX spectroscopy-data-format compliance, and ISO-and-EN scientific publication. A 13.6 eV hydrogen-Lyman-alpha ionisation-energy translates to 2.18 × 10⁻¹⁸ J; a 4.7 eV hydrogen-bond-dissociation-energy translates to 7.53 × 10⁻¹⁹ J; a 5.14 eV sodium-ionisation-energy translates to 8.24 × 10⁻¹⁹ J. The conversion runs at every atomic-and-molecular-spectroscopy-eV source to chemistry-engineering-J documentation step.
Solar-cell photon-energy eV translated to J for photovoltaic-engineering quantum-efficiency documentation
Solar-cell photovoltaic-engineering photon-energy specifications expressed in eV translate to J for photovoltaic-engineering quantum-efficiency calculations, solar-spectrum integration, and ISO-and-IEC photovoltaic-equipment documentation. A 1.0 eV near-infrared photon translates to 1.602 × 10⁻¹⁹ J; a 2.0 eV visible-light photon translates to 3.20 × 10⁻¹⁹ J; a 3.5 eV near-ultraviolet photon translates to 5.61 × 10⁻¹⁹ J. The conversion runs at every solar-cell-photon-eV source to photovoltaic-engineering-J documentation step.
When to use Joules instead of Electron-volts
Use joules whenever the destination is SI scientific-and-engineering documentation, macroscopic-scale physics-engineering work, ISO-and-EN compliance harmonisation, JCAMP-DX spectroscopy-data-format compliance, photovoltaic-engineering quantum-efficiency calculations, or any context where the SI energy primary is required. The joule is the universal SI-derived energy unit anchored to the kilogram-metre-second chain via the Planck constant. Stay in electronvolts when the destination is atomic-and-molecular physics, particle-physics-accelerator beam-energy specifications, semiconductor-device band-gap engineering, atomic-and-molecular spectroscopy transition-energy documentation, or any microscopic-scale physics-engineering context where eV-and-keV-and-MeV-and-GeV-and-TeV-scale granularity matches the underlying physics. The conversion is the universal microscopic-to-macroscopic energy scale-shift between physics-eV-source and engineering-J-destination documentation, applied at every cross-disciplinary physics-and-engineering documentation boundary across semiconductor, particle-physics, atomic-spectroscopy, and photovoltaic-engineering work.
Common mistakes converting eV to J
- Treating "1 eV = 1 J" as a rough equivalence. The two units differ by a factor of about 1.6 × 10⁻¹⁹ — substituting one for the other gives an error of nineteen orders of magnitude. The correct factor is 1 eV = 1.602176634 × 10⁻¹⁹ J exactly.
- Confusing eV (electronvolt, energy) with V (volt, potential difference). The two share the "volt" name root but represent different quantities — energy versus potential. One eV is the kinetic energy gained by an electron accelerated through 1 V potential difference, hence the connection, but eV cannot be substituted for V or vice versa in dimensional-analysis calculations.
Frequently asked questions
How many joules in 1 eV?
One electronvolt equals exactly 1.602176634 × 10⁻¹⁹ joules, derived from the elementary charge e = 1.602176634 × 10⁻¹⁹ C exactly via the 2019 SI redefinition. The factor is fixed by definition rather than measured. The "1 eV ≈ 1.602 × 10⁻¹⁹ J" reference is universal in modern atomic-and-molecular-and-particle-and-semiconductor physics work for converting eV-scale energy figures to SI joule notation.
How many joules in 1.12 eV (silicon band-gap)?
One point one two electronvolts equals 1.795 × 10⁻¹⁹ joules. That is the silicon-semiconductor band-gap energy translated to SI device-engineering documentation. The eV-figure sits on the semiconductor-physics primary specification and the J-figure sits on the SI device-engineering reference for solid-state-electronics work under ISO and EN conventions.
How many joules in 13.6 eV (hydrogen ionisation)?
Thirteen point six electronvolts equals 2.18 × 10⁻¹⁸ joules. That is the hydrogen-atom Lyman-alpha ionisation-energy translated to SI chemistry-engineering documentation. The eV-figure sits on the atomic-physics primary specification and the J-figure sits on the SI chemistry-engineering reference for atomic-and-molecular spectroscopy work.
Quick way to convert eV to J in my head?
Multiply the eV figure by 1.6 × 10⁻¹⁹ — the approximation is within 0.13% of exact. For 1 eV that gives about 1.6 × 10⁻¹⁹ J, for 10 eV that gives about 1.6 × 10⁻¹⁸ J, for 1 keV (1000 eV) that gives about 1.6 × 10⁻¹⁶ J, for 1 MeV that gives about 1.6 × 10⁻¹³ J, for 1 GeV that gives about 1.6 × 10⁻¹⁰ J. The exact factor is 1.602176634 × 10⁻¹⁹.
What is the difference between eV and J?
Both are units of energy. The electronvolt (eV) is the natural microscopic-scale energy unit for atomic-and-molecular-and-particle-and-semiconductor physics, where the relevant energies are around 1 eV (chemical bonds) to 1 TeV (particle-physics-accelerator beams). The joule (J) is the SI macroscopic-scale energy unit for everyday-and-engineering work. The two differ by 19 orders of magnitude (1 eV ≈ 1.6 × 10⁻¹⁹ J), so each is the natural unit at its scale.
When does eV-to-J conversion appear in real work?
It appears in semiconductor band-gap eV translated to J for solid-state physics and device-engineering documentation and in particle-physics beam-energy GeV-and-TeV translated to J for accelerator-physics-engineering documentation. It also appears in atomic-and-molecular spectroscopy eV translated to J for chemistry-engineering and JCAMP-DX format and in solar-cell photon-energy eV translated to J for photovoltaic-engineering quantum-efficiency documentation. The conversion is one of the most-run microscopic-to-macroscopic energy conversions in modern physics-and-engineering work.
How precise should eV-to-J be for engineering work?
For engineering work the eV-to-J conversion is exact (factor 1.602176634 × 10⁻¹⁹ exactly via the 2019 SI redefinition), and the precision allowance comes from the underlying source-measurement precision rather than the conversion itself. Most engineering documentation rounds to four significant figures (1 eV ≈ 1.602 × 10⁻¹⁹ J), which is sufficient for typical semiconductor, atomic-physics, and particle-physics applications. Higher-precision applications (atomic-clock metrology, fundamental-physics) preserve more digits.