Kilojoules to Joules (kJ to J) Converter
1 kilojoule equals 1000 joules — multiply the number of kilojoules by 1000 to convert to joules. Both are SI energy units, and because "kilo" means one thousand the relationship is exact.
The formula
To convert kilojoules to joules, multiply by 1000:
joules = kilojoules × 1000
For example, 3.5 kJ × 1000 = 3500 J. To reverse, divide joules by 1000.
Conversion table
| Kilojoules (kJ) | Joules (J) |
|---|---|
| 1 | 1000 |
| 2 | 2000 |
| 5 | 5000 |
| 10 | 10000 |
| 25 | 25000 |
| 50 | 50000 |
| 100 | 100000 |
| 500 | 500000 |
| 1000 | 1000000 |
How to convert online
- Type the number of kilojoules into the first box.
- Read the equivalent joules instantly in the second box.
- Or enter a joule value to convert back to kilojoules — it works both ways.
Use the Kilojoule to Joule Converter — free and instant in your browser.
Where this conversion is used
Joules are the base SI unit of energy and work, so this conversion is a staple of physics homework, engineering calculations, thermodynamics and mechanics. Energy is often stated in kilojoules for readability but must be reduced to joules to combine with force, power and other SI quantities in a formula.
FAQ
How many joules are in a kilojoule?
Exactly 1000 joules. So 7 kJ = 7000 J.
What is the formula to convert kilojoules to joules?
J = kJ × 1000. The converter applies the exact factor automatically.
How do I convert joules back to kilojoules?
Divide by 1000, or multiply by 0.001. For example, 4500 J = 4.5 kJ.
Is the conversion exact?
Yes. The factor of 1000 is definitional, so results are always precise with no rounding.
Related converters
- Joule to Kilojoule Converter
- Kilojoule to Calorie Converter
- Kilojoule to Kilocalorie Converter
- Kilojoule to Kilowatt-hour Converter
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