Electronvolts to Kilojoules Converter
Common Conversions
| eV | kJ |
|---|---|
| 1 | 1.602e-22 |
| 10 | 1.602e-21 |
| 100 | 1.602e-20 |
| 1000 | 1.602e-19 |
| 10000 | 1.602e-18 |
| 100000 | 1.602e-17 |
| 1000000 | 1.602e-16 |
| 1000000000 | 1.602e-13 |
| 1000000000000 | 1.602e-10 |
| 1000000000000000 | 1.602e-7 |
| 1000000000000000000 | 0.0001602 |
| 1e+21 | 0.1602 |
Why this conversion matters in chemistry
An electronvolt is one electron's worth of charge moved through one volt — a tiny energy at the macroscopic scale (1 eV is 1.602 × 10⁻²² kJ) but the natural unit for individual photons, electrons, and molecular orbitals. The mole-scale conversion is much more useful: 1 eV per particle equals 96.485 kJ/mol, which is just Avogadro's number times the elementary charge expressed as kJ. The conversion is the bridge between a UV-visible band gap, a DFT energy, or an X-ray transition reported in eV and a thermochemistry table written in kJ/mol. Hematite's 2.1 eV band gap, for instance, sits comfortably above the 1.23 eV thermodynamic minimum per electron for water splitting — but real overpotentials and recombination losses are why hematite still needs an external bias to drive the reaction.
Formula
Where the factor comes from
This pair is the electronvolt-to-joule identity with a kilo hung on the far side, and the kilo is where all the character lives. One eV is exactly 1.602176634 × 10⁻¹⁹ J through the fixed elementary charge; divide by 1000 and you have exactly 1.602176634 × 10⁻²² kJ. Both halves are defined, so nothing in the chain was ever measured. What makes the combination odd is that it hangs a laboratory-scale prefix on an atomic-scale quantity — a kilojoule is an energy you can feel as heat, and one electronvolt is 6.2 × 10²¹ times smaller. Most published work skips this form and goes to kJ per mole instead, where Avogadro's number lifts the exponent back into the range chemists actually reason with.
Precision and significant figures
In this pair the mantissa is rarely what goes wrong; the exponent is. 1.602 × 10⁻²² and 1.602 × 10⁻¹⁹ look identical at a glance and differ by a thousand, the sort of slip that survives a careful proofread. Three or four figures on the mantissa is ample, since no eV measurement arrives with more, and the factor is defined rather than measured so it never sets the limit itself. The other hazard is formatting rather than arithmetic: a spreadsheet column set to two decimals in scientific notation reports three significant figures regardless of what was entered, so precision present in the source quietly vanishes from the report.
Worked Examples
One electronvolt for a single particle — vanishingly small at the macroscopic scale, which is why mol-based conversion is the practical move.
The number of electronvolts that add up to one kilojoule — equivalently, 0.01 mol of single-eV events.
The ionization energy of a single hydrogen atom — the Rydberg energy, the foundational atomic-physics number.
One keV — the photon energy range where soft X-ray and core-level photoemission spectroscopy operate.
Common mistakes
Kilo sits on the joule, not the eV
The prefix in this conversion belongs to the output. A keV input is 1000 eV and still needs the 10⁻²² factor, landing at 1.602 × 10⁻¹⁹ kJ. Writing 1 keV as 1.602 kJ because both terms carry a kilo is wrong by nineteen decades, and it is a genuine slip once both prefixes appear on the same worksheet line.
Mixing per-particle and per-mole terms
An energy balance that adds a per-particle kilojoule to a reaction enthalpy in kJ/mol is dimensionally broken even though both terms read as kJ. The per-mole term is 10²³ times larger and simply swallows the other without complaint. Keep the /mol attached to the label all the way through; the moment it gets dropped for tidiness, the check that would have caught this is gone.
Photon energy is not photon dose
A 3 eV photon is 4.807 × 10⁻²² kJ, while a photoreactor's output is quoted in watts, or its delivery in einsteins. Getting between them needs the photon flux, not a unit conversion: divide the delivered energy in kJ by the per-photon value to count photons, then by Avogadro's number for moles of photons. This factor supplies one link in that chain, not the answer.