How to convert joules to kilojoules
To convert joules to kilojoules, multiply by 0.001. Energy conversions connect nutrition, electricity bills, heating systems and physics.
Joule to Kilojoule conversion table
| Joule (J) | Kilojoule (kJ) |
|---|---|
| 0.1 J | 0.0001 kJ |
| 0.5 J | 0.0005 kJ |
| 1 J | 0.001 kJ |
| 2 J | 0.002 kJ |
| 3 J | 0.003 kJ |
| 4 J | 0.004 kJ |
| 5 J | 0.005 kJ |
| 10 J | 0.01 kJ |
| 20 J | 0.02 kJ |
| 25 J | 0.025 kJ |
| 50 J | 0.05 kJ |
| 100 J | 0.1 kJ |
| 500 J | 0.5 kJ |
| 1,000 J | 1 kJ |
About the units
Joule (J)
The joule is the SI unit of energy, the work done by one newton over one meter.
Kilojoule (kJ)
A kilojoule is 1,000 joules and appears on food labels in many countries.
How to use this converter
- Type the number of joules (J) in the input box.
- The result in kilojoules appears instantly — no button needed.
- See the same value in every other energy unit just below.
- Use “Swap units” to convert kilojoules back to joules.
Tips for better results
- Double-check which system a unit belongs to (for example US vs UK gallons).
- Use the swap button to convert in the opposite direction instantly.
- Bookmark the conversions you use most — each pair has its own page.
Frequently asked questions
How many kilojoules are in one joule?
One joule equals 0.001 kilojoules. 0.001 is the exact factor used by this converter.
How do I convert joules to kilojoules?
Multiply the value in joules by 0.001. To go the other way, multiply kilojoules by 1,000.
What is 10 J in kJ?
10 J = 0.01 kJ. Also, 5 J = 0.005 kJ and 100 J = 0.1 kJ.
What is the difference between a joule and a kilojoule?
The joule is the SI unit of energy, the work done by one newton over one meter. A kilojoule is 1,000 joules and appears on food labels in many countries.
Is this tool free and private?
Yes — the Joule to Kilojoule is completely free with no sign-up, and it runs entirely in your browser, so the values you enter are never uploaded to our servers.
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