Joules to Electron-volts (J to eV)
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Joules-to-electronvolts conversions translate SI macroscopic-scale physics-and-engineering energy figures into the eV-and-keV-and-MeV-and-GeV-and-TeV scale used for atomic-and-molecular, particle-physics-accelerator, semiconductor-device, and atomic-spectroscopy work. A 1.795 × 10⁻¹⁹ J SI engineering figure translates to 1.12 eV silicon-semiconductor band-gap on the semiconductor-physics documentation; a 2.18 × 10⁻¹⁸ J chemistry-figure translates to 13.6 eV hydrogen-ionisation-energy on the atomic-physics reference; a 1.12 × 10⁻⁶ J accelerator-engineering figure translates to 7 TeV LHC-beam-energy on the particle-physics documentation. The factor is exact at 1 J = 6.241509074... × 10¹⁸ eV, the multiplicative inverse of the eV-to-J conversion fixed by the 2019 SI redefinition.
How to convert Joules to Electron-volts
Formula
eV = J × 6.241509 × 10¹⁸
To convert joules to electronvolts, multiply the J figure by 6.241509074... × 10¹⁸ — exactly, the multiplicative inverse of the eV-to-J factor fixed by the 2019 SI redefinition. For mental math, treat the factor as 6.24 × 10¹⁸ for everyday physics work — the approximation is exact to the cited precision. Practical scale references: 10⁻¹⁹ J ≈ 0.624 eV, 10⁻¹⁸ J ≈ 6.24 eV, 10⁻¹⁶ J ≈ 624 eV ≈ 0.624 keV, 10⁻¹³ J ≈ 0.624 MeV, 10⁻¹⁰ J ≈ 0.624 GeV. The conversion runs at every SI-J source to atomic-and-molecular-and-particle-and-semiconductor physics-eV destination boundary, with the factor exact rather than measured.
Worked examples
Example 1 — 1 J
One joule equals 6.241509074... × 10¹⁸ electronvolts, the multiplicative inverse of the eV-to-J factor fixed by the 2019 SI redefinition. The factor is exact rather than measured.
Example 2 — 1.795e-19 J
One point seven nine five times ten-to-the-minus-nineteen joules — the SI-equivalent of the silicon-semiconductor band-gap — converts to 1.12 eV on the device-physics documentation. The J-figure is the SI device-engineering primary; the eV-figure is the semiconductor-physics reference.
Example 3 — 2.18e-18 J
Two point one eight times ten-to-the-minus-eighteen joules — the SI-equivalent of the hydrogen-atom ionisation-energy — converts to 13.6 eV on the atomic-physics documentation. The J-figure is the SI chemistry-engineering primary; the eV-figure is the atomic-and-molecular-physics reference.
J to eV conversion table
| J | eV |
|---|---|
| 1 J | 6241509074460763136 eV |
| 2 J | 12483018148921526272 eV |
| 3 J | 18724527223382290432 eV |
| 4 J | 24966036297843052544 eV |
| 5 J | 31207545372303814656 eV |
| 6 J | 37449054446764580864 eV |
| 7 J | 43690563521225342976 eV |
| 8 J | 49932072595686105088 eV |
| 9 J | 56173581670146867200 eV |
| 10 J | 62415090744607629312 eV |
| 15 J | 93622636116911439872 eV |
| 20 J | 124830181489215258624 eV |
| 25 J | 156037726861519093760 eV |
| 30 J | 187245272233822879744 eV |
| 40 J | 249660362978430517248 eV |
| 50 J | 312075453723038187520 eV |
| 75 J | 468113180584557215744 eV |
| 100 J | 624150907446076375040 eV |
| 150 J | 936226361169114431488 eV |
| 200 J | 1.2483018148921528e+21 eV |
| 250 J | 1.5603772686151907e+21 eV |
| 500 J | 3.1207545372303814e+21 eV |
| 750 J | 4.6811318058455726e+21 eV |
| 1000 J | 6.241509074460763e+21 eV |
| 2500 J | 1.5603772686151908e+22 eV |
| 5000 J | 3.1207545372303816e+22 eV |
Common J to eV conversions
- 1e-19 J=0.6242 eV
- 1e-18 J=6.2415 eV
- 1e-16 J=624.1509 eV
- 1e-13 J=624150.9074 eV
- 1e-10 J=624150907.4461 eV
- 1.795e-19 J=1.1204 eV
- 2.18e-18 J=13.6065 eV
- 1.602e-19 J=0.9999 eV
- 5.45e-19 J=3.4016 eV
- 1.06e-19 J=0.6616 eV
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.
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.
Real-world uses for Joules to Electron-volts
SI semiconductor-engineering J translated to eV for device-physics band-gap and carrier-energy documentation
SI semiconductor-engineering energy figures from device-simulation and characterisation translate to eV for device-physics band-gap, carrier-energy, and IEEE-and-ISO semiconductor-engineering documentation. A 1.795 × 10⁻¹⁹ J translates to 1.12 eV silicon band-gap; a 5.45 × 10⁻¹⁹ J translates to 3.4 eV gallium-nitride band-gap; a 1.06 × 10⁻¹⁹ J translates to 0.66 eV germanium band-gap. The conversion runs at every SI-J device-simulation source to eV semiconductor-physics-documentation step in modern semiconductor-engineering work.
SI accelerator-engineering J translated to GeV-and-TeV for particle-physics-facility documentation
SI accelerator-engineering beam-energy-and-power figures translate to GeV-and-TeV for particle-physics-facility documentation under CERN-Fermilab-KEK-and-similar conventions, where GeV-and-TeV are the universal particle-physics scale. A 1.12 × 10⁻⁶ J translates to 7 TeV LHC proton-beam energy; a 4.81 × 10⁻⁷ J translates to 3 TeV collision-energy; a 1.6 × 10⁻¹⁰ J translates to 1 GeV cyclotron-beam-energy. The conversion runs at every SI-J accelerator-engineering source to GeV-and-TeV particle-physics-facility documentation step.
SI chemistry-and-spectroscopy J translated to eV for atomic-and-molecular-physics documentation
SI chemistry-engineering and spectroscopy energy figures from JCAMP-DX-and-ISO-and-EN scientific publication translate to eV for atomic-and-molecular-physics transition-energy documentation, where eV is the natural atomic-and-molecular-physics scale. A 2.18 × 10⁻¹⁸ J translates to 13.6 eV hydrogen-ionisation; a 7.53 × 10⁻¹⁹ J translates to 4.7 eV hydrogen-bond-dissociation; a 8.24 × 10⁻¹⁹ J translates to 5.14 eV sodium-ionisation. The conversion runs at every SI-J chemistry-and-spectroscopy source to eV atomic-and-molecular-physics-documentation step.
SI photovoltaic-engineering J translated to eV for solar-cell quantum-efficiency-and-bandgap-matching documentation
SI photovoltaic-engineering energy figures from solar-cell device-simulation and quantum-efficiency-measurement translate to eV for solar-cell-bandgap-matching documentation under ISO-and-IEC photovoltaic-equipment conventions. A 1.602 × 10⁻¹⁹ J translates to 1.0 eV near-infrared photon-energy; a 3.20 × 10⁻¹⁹ J translates to 2.0 eV visible-light-photon-energy; a 5.61 × 10⁻¹⁹ J translates to 3.5 eV near-ultraviolet photon-energy. The conversion runs at every SI-J photovoltaic-engineering source to eV solar-cell-bandgap-documentation step.
When to use Electron-volts instead of Joules
Use electronvolts whenever 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, photovoltaic-engineering bandgap-matching, or any microscopic-scale physics-engineering context where eV-and-keV-and-MeV-and-GeV-and-TeV-scale granularity matches the underlying physics. The eV-and-multiples-figure is the natural microscopic-scale energy unit, with prefix-multipliers spanning twenty-one orders of magnitude. Stay in joules when the destination is SI macroscopic-scale physics-engineering work, ISO-and-EN compliance harmonisation, JCAMP-DX spectroscopy-data-format compliance, or any SI scientific context where J-and-kJ-and-MJ is the primary unit. The conversion is the universal macroscopic-to-microscopic energy scale-shift between SI-engineering-J-source and physics-eV-destination documentation, applied across semiconductor-device, particle-physics-accelerator, atomic-and-molecular-spectroscopy, and photovoltaic-engineering documentation work in modern cross-disciplinary physics-and-engineering pipelines globally.
Common mistakes converting J to eV
- Treating "1 J = 1 eV" as a rough equivalence. The two units differ by 19 orders of magnitude — substituting one for the other gives an error of nineteen orders of magnitude. The correct factor is 1 J = 6.241509 × 10¹⁸ eV exactly.
- Forgetting to apply prefix-multipliers correctly when working with keV-and-MeV-and-GeV-and-TeV scales. A "1 keV" figure is 1000 eV which is 1.602 × 10⁻¹⁶ J, not 1.602 × 10⁻¹⁹ J. The prefix-multipliers (k, M, G, T) on eV correspond to factors of 10³, 10⁶, 10⁹, 10¹² respectively, with each three-decade-shift requiring care in the J conversion.
Frequently asked questions
How many eV in 1 J?
One joule equals 6.241509074... × 10¹⁸ electronvolts, the multiplicative inverse of the eV-to-J factor fixed by the 2019 SI redefinition that set the elementary charge e = 1.602176634 × 10⁻¹⁹ C exactly. The factor is exact rather than measured. The "1 J ≈ 6.24 × 10¹⁸ eV" reference is universal in modern macroscopic-to-microscopic energy conversion in physics-and-engineering work.
How many eV in 1.795 × 10⁻¹⁹ J (silicon band-gap)?
One point seven nine five times ten-to-the-minus-nineteen joules equals 1.12 eV. That is the SI-equivalent of the silicon-semiconductor band-gap energy translated to device-physics documentation. The J-figure sits on the SI device-engineering primary; the eV-figure sits on the semiconductor-physics reference for solid-state-electronics work under IEEE and ISO conventions.
How many eV in 2.18 × 10⁻¹⁸ J (hydrogen ionisation)?
Two point one eight times ten-to-the-minus-eighteen joules equals 13.6 eV. That is the SI-equivalent of the hydrogen-atom Lyman-alpha ionisation-energy translated to atomic-physics documentation. The J-figure sits on the SI chemistry-engineering primary; the eV-figure sits on the atomic-and-molecular-physics reference for spectroscopy-and-quantum-mechanics work.
Quick way to convert J to eV in my head?
Multiply the J figure by 6.24 × 10¹⁸ for everyday physics work. Practical scale references: 10⁻¹⁹ J ≈ 0.624 eV, 10⁻¹⁸ J ≈ 6.24 eV, 10⁻¹⁶ J ≈ 0.624 keV, 10⁻¹³ J ≈ 0.624 MeV, 10⁻¹⁰ J ≈ 0.624 GeV, 10⁻⁷ J ≈ 0.624 TeV. The exact factor is 6.241509 × 10¹⁸, with the natural prefix-multipliers landing at three-decade-shifts.
How many J 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.
When does J-to-eV conversion appear in real work?
It appears in SI semiconductor-engineering J translated to eV for device-physics band-gap and carrier-energy documentation and in SI accelerator-engineering J translated to GeV-and-TeV for particle-physics-facility documentation. It also appears in SI chemistry-and-spectroscopy J translated to eV for atomic-and-molecular-physics documentation and in SI photovoltaic-engineering J translated to eV for solar-cell quantum-efficiency-and-bandgap-matching documentation. The conversion is one of the most-run macroscopic-to-microscopic energy conversions in modern physics-and-engineering work.
How precise should J-to-eV be for engineering work?
For engineering work the J-to-eV conversion is exact (factor 6.241509074 × 10¹⁸ 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 J ≈ 6.242 × 10¹⁸ eV), which is sufficient for typical semiconductor, atomic-physics, and particle-physics applications. Higher-precision applications preserve more digits.