Joules to Electronvolts

Joules and electronvolts

The joule is the SI unit of energy: the work done by a force of one newton over one meter, or one watt for one second. Physics, engineering and EU food labels (as kJ) use joules.

The electronvolt is the energy an electron gains across one volt: exactly 1.602176634 × 10⁻¹⁹ joules since 2019. Particle physics, chemistry and semiconductor band gaps use electronvolts.

Worked example

Convert 1 × 10^-18 J: 1 × 10^-18 × 6.241509074 × 10^18 = 6.241509074, so 1 × 10^-18 joules is 6.241509074 electronvolts. Likewise 2 × 10^-18 J = 12.48301815 eV.

Estimating in your head

Multiply by 6.2 × 10^18 for a quick figure; it is off by about 0.7%. For 1 × 10^-18 J that gives 6.2 × 10^-18 eV, against 6.24151 exactly.

Going the other way

To convert electronvolts to joules, divide by 6.241509074 × 10^18 (or multiply by 1.602176634 × 10^-19). The swap button between the boxes opens that page.

eV = J × 6.241509074 × 10^18

1 J = 1 J and 1 eV = 1.602176634 × 10^-19 J, both by definition, so the factor is their ratio: 6.241509074 × 10^18 (rounded here; the page uses the full value). Results drop binary floating-point noise beyond 15 significant digits and display at the precision you choose (6 significant figures by default). Copy result copies the full value.