How to convert joules to kilojoules
kJ = J × 0.001Multiply the value in joules by 0.001. To go the other way, multiply by 1,000 (or divide by 0.001).
A joule is smaller than a kilojoule: it takes 1,000 joules to make one kilojoule.
Worked examples
- 1 joule1 J × 0.001 = 0.001 kJ
- 5 joules5 J × 0.001 = 0.005 kJ
- 10 joules10 J × 0.001 = 0.01 kJ
- 20 joules20 J × 0.001 = 0.02 kJ
- 100 joules100 J × 0.001 = 0.1 kJ
Joules to kilojoules conversion table
Values are calculated by the conversion engine and rounded to 8 significant figures.
| Joules (J) | Kilojoules (kJ) |
|---|---|
| 0.1 J | 0.0001 kJ |
| 0.25 J | 0.00025 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 |
| 6 J | 0.006 kJ |
| 7 J | 0.007 kJ |
| 8 J | 0.008 kJ |
| 9 J | 0.009 kJ |
| 10 J | 0.01 kJ |
| Joules (J) | Kilojoules (kJ) |
|---|---|
| 12 J | 0.012 kJ |
| 15 J | 0.015 kJ |
| 20 J | 0.02 kJ |
| 25 J | 0.025 kJ |
| 30 J | 0.03 kJ |
| 40 J | 0.04 kJ |
| 50 J | 0.05 kJ |
| 75 J | 0.075 kJ |
| 100 J | 0.1 kJ |
| 250 J | 0.25 kJ |
| 500 J | 0.5 kJ |
| 1,000 J | 1 kJ |
About the units
Joule (J)
The SI unit of energy: the work done by a force of one newton over one metre, or one watt for one second. Lifting an apple by one metre takes about 1 J.
Kilojoule (kJ)
One thousand joules. Food labels in Australia and the EU list energy in kJ alongside kcal. One kilojoule equals 1,000 joules (J).
Frequently asked questions
How many kilojoules are in one joule?
There are 0.001 kilojoules in one joule, and this value is exact by definition.
How do I convert joules to kilojoules?
Multiply the number of joules by 0.001. For example, 10 J × 0.001 = 0.01 kJ.
How many joules are in one kilojoule?
One kilojoule equals 1,000 joules. That is the reverse factor, 1 ÷ 0.001.
What is 10 joules in kilojoules?
10 J = 0.01 kJ.
Is this J to kJ converter accurate?
Yes. Both units are defined exactly in terms of SI units, so the conversion factor is exact; results are shown to 12 significant figures by default and you can change precision in the converter. Calculations run in your browser using the same tested engine that generated this page.