Kilojoules to joules
Multiply kilojoules by 1,000 to get joules.
5 kJ = 5,000 J
How to convert kilojoules to joules
The joule is the SI unit of energy, one newton-metre (one watt for one second). The kilojoule is one thousand joules — the metric food-energy unit used outside the US.
Worked example — 5 kJ: 5 × 1,000 = 5,000 J.
Kilojoules to joules table
| Kilojoules | Joules |
|---|---|
| 0.1 kJ | 100 J |
| 0.5 kJ | 500 J |
| 1 kJ | 1,000 J |
| 2 kJ | 2,000 J |
| 5 kJ | 5,000 J |
| 10 kJ | 10,000 J |
| 50 kJ | 50,000 J |
| 100 kJ | 100,000 J |
| 500 kJ | 500,000 J |
Reverse and related
About kilojoules and joules
Kilojoule (kJ)
1 kJ = 1,000 JDefinition. One thousand joules — the metric food-energy unit used outside the US
History and origin
The kilojoule is one thousand joules, the metric unit of energy built on the SI joule. It is the food-energy unit preferred where the metric system is standard.
Current use
Kilojoules are used on nutrition labels outside the United States and throughout physics and engineering.
Source: NIST SP 811, Appendix B; ISO 80000-5 (energy)
Joule (J)
1 J = 0.001 kJDefinition. The SI unit of energy, one newton-metre (one watt for one second)
History and origin
The joule is the SI unit of energy, named after James Prescott Joule, who showed in the 1840s that heat and mechanical work are equivalent. It is the work done by one newton acting over one metre.
Current use
Joules are the standard energy unit in physics and appear on appliance and equipment ratings.
Source: NIST SP 811, Appendix B; ISO 80000-5 (energy)
Where people use this
Kilojoules: nutrition labels outside the US, physics. Joules: physics, appliance ratings. 1 kJ is exactly 1000 J.
Every value is carried to full double precision; the display is rounded.
Both units are defined in NIST SP 811, Appendix B; ISO 80000-5 (energy).
Questions people ask
How many joules in a kJ?
One kilojoule is exactly 1000 joules.
How many joules is 2 kJ?
2 kJ is 2000 joules.
How many kJ is 500 J?
500 J is 0.5 kJ.