Convert joules to kilojoules
Converting joules to kilojoules is a common energy task, whether you are checking a recipe, a spec sheet, a travel distance or a homework problem. Since 1 J equals 0.001 kJ, the math is a single multiplication — and this page does it for you instantly, with the formula, a table of common values and answers to the questions people ask most.
Exact factor
How to convert joules to kilojoules
To convert joules to kilojoules, multiply the number of joules by 0.001. For example, 10 J × 0.001 = 0.01 kJ.
kJ = J × 0.001
- Write down the value in joules you want to convert.
- Multiply it by 0.001 (the exact J→kJ factor).
- The result is your value in kilojoules. Check it below with the converter or the table.
Conversion table
Common values of joules and their equivalents in kilojoules:
| J | kJ |
|---|---|
| 1 | 0.001 |
| 2 | 0.002 |
| 3 | 0.003 |
| 4 | 0.004 |
| 5 | 0.005 |
| 10 | 0.01 |
| 20 | 0.02 |
| 25 | 0.025 |
| 50 | 0.05 |
| 100 | 0.1 |
| 250 | 0.25 |
| 500 | 0.5 |
About these units
Joule (J). The joule is the SI unit of energy: the work done by one newton acting over one meter. Food labels in most countries, physics and engineering use joules.
Kilojoule (kJ). A kilojoule is 1,000 joules, the practical unit for food energy in Australia and Europe and for mechanical work. One kilocalorie equals 4.184 kilojoules.
Frequently asked questions
How do I convert joules to kilojoules?
To convert joules to kilojoules, multiply the number of joules by 0.001. For example, 10 J × 0.001 = 0.01 kJ. Or skip the math: type the value into the converter at the top of this page and the result updates instantly.
How many kilojoules are in 1 joule?
1 J = 0.001 kJ. That is the fixed relationship used by this converter and by international standards.
How many joules are in 1 kilojoule?
1 kJ = 1,000 J. If you are converting in the opposite direction, use our Kilojoule to Joule converter for the dedicated table and FAQ.
Is the joules to kilojoules conversion exact?
Yes. Both units are defined by international agreement, so the factor of 0.001 is exact. Displayed results are rounded to 6 significant digits only for readability.
What is joule used for?
The joule is the SI unit of energy: the work done by one newton acting over one meter. Food labels in most countries, physics and engineering use joules.