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Joules to Electronvolts Converter
1 J = 6.241509074 × 10¹⁸ eV.
—
Six point two four times ten to the eighteen
One joule is 6.241509074 × 1018 electronvolts — the reciprocal of the elementary charge.
1 J = 6.241509074 × 1018 eV
That figure is also the number of electrons carrying one coulomb of charge, which is not a coincidence: the electronvolt is defined from the same constant.
Going this way is usually about making a macroscopic energy meaningful at atomic scale, or checking that a result from an SI calculation lands in a plausible eV range.
The joule
The SI unit of energy: the work done when a force of one newton moves something one metre. It is a small unit — lifting an apple a metre off the table takes about one joule.
Everything else on this page is the same quantity counted differently. A joule is also one watt for one second, which is the link between energy and power.
The electronvolt
The energy an electron gains crossing a potential difference of one volt. Since the 2019 redefinition of SI it is exactly 1.602176634 × 10−19 joules, because the elementary charge is now a defined constant.
It is the natural unit for atomic and particle physics. Visible light photons carry 1.6 to 3.3 eV; chemical bonds are a few eV; particle accelerators work in giga- and tera-electronvolts.
The working, step by step
Every line updates with whatever you type above. The point is the method, which is the same for any pair of units in this family.
The same quantity, two different numbers
One physical amount, read off two scales. The tick marks do not line up, and the gap between them is the conversion factor made visible.
Your turn
Reading a method and being able to use it are different things. Answer within half a per cent and it counts as correct.
Score: 0 of 0
How to use this converter
- Type into either box. The other side updates as you go; there is no button to press.
- Swap the direction with the button between the boxes, carrying your value across.
- Set the decimals if the default is more or less precision than you need.
- Copy the answer with its unit, ready to paste.
- Use the shortcut buttons for the values that come up most often.
- Share the result. The address bar tracks what you type, so the link you copy opens on the same number.
Common uses and tips
Where this comes up
- Food labels. Europe and Australia print kilojoules; the United States prints Calories. The same packet often carries both.
- Nutrition and exercise tracking, where one app reports kJ and another kcal.
- Chemistry and physics coursework, where reaction enthalpies come in kJ/mol and older texts use calories.
- Physics at atomic scale, where electronvolts are the only sensible size.
The trap: calorie and Calorie
The word means two things a thousand apart.
- calorie (small c) — the scientific unit, exactly 4.184 joules. Enough to warm a gram of water by one degree.
- Calorie (capital C), or kcal — a thousand of those, 4,184 joules. This is what every food label means.
So a 2,000-Calorie daily intake is 2,000 kcal, which is 2,000,000 small calories, or 8.37 megajoules. If a conversion comes out a thousand away from what you expected, this is why.
Tips worth knowing
- 4.184 is the number to remember. It works at every scale: cal to J, kcal to kJ, Mcal to MJ.
- Energy is not power. Joules are an amount; watts are a rate. They cannot be converted without a time.
- A kilowatt-hour is energy, not power: 3.6 MJ, or 860 kcal.
Values people look up most
Each one opens the converter with the number already in it.
- 0 J to eV
- 0 J to eV
- 0 J to eV
- 0 J to eV
- 0 J to eV
- 0.000000001 J to eV
- 0.000001 J to eV
- 0.001 J to eV
- 1 J to eV
Quick reference
| Joules | Electronvolts |
|---|---|
| 0 J | 0.624151 eV |
| 0 J | 6.241509 eV |
| 0 J | 6,241.509074 eV |
| 0 J | 6,241,509.074461 eV |
| 0.000000001 J | 6,241,509,074.4607639313 eV |
| 0.000001 J | 6,241,509,074,460.7626953125 eV |
| 1 J | 6,241,509,074,460,763,136 eV |
Questions people ask
How many electronvolts in a joule?
6.241509074 × 10¹⁸ eV.
Is that the same as the number of electrons in a coulomb?
Yes. Both come from the elementary charge, which is why the figures match.
When would I need this?
Mostly when checking that an SI calculation gives a sensible atomic scale answer.