Convert Kilojoules to Joules
1 kilojoule is 1,000 J. One kilojoule is exactly 1000 joules.
One kilojoule is 1000 joules. To convert kilojoules to joules, multiply by 1000; to go the other way, divide by 1000 or multiply by 0.001. The factor is exact rather than rounded: it follows from NIST Special Publication 811. A thousand joules.
Factor checked against the defining standard · How we check
- Kilojoules × 1000
value * 10001,000 J
1 kilojoule in every energy unit
| Unit | Value | Exact factor |
|---|---|---|
| joules | 1,000 J | × 1,000 |
| kilojoules (as entered) | 1 kJ | — |
| calories | 239.0057361 cal | × 239.005736138 |
| kilocalories | 0.2390057361 kcal | × 0.239005736138 |
| watt-hours | 0.2777777778 Wh | × 0.277777777778 |
| kilowatt-hours | 0.0002777777778 kWh | × 0.000277777777778 |
| British thermal units | 0.9478171203 BTU | × 0.947817120313 |
| foot-pounds | 737.5621493 ft·lbf | × 737.562149277 |
Factors are entered by hand from NIST Special Publication 811 rather than derived from a units library, so the ones that terminate are exact rather than rounded.
How do you convert kilojoules to joules?
- 1.Take the measurement in kilojoules.
- 2.Multiply by 1000 — that is how many joules fit in one kilojoule.
- 3.To go back the other way, divide by 1000, or multiply by 0.001.
Worked example: 25 kilojoules to joules
- Formula
- kJ × 1000 = J
- Arithmetic
- 25 × 1000 = 25,000 J
- Answer
- 25 kJ = 25,000 J
The factor is exact, so this figure is exact too — only the display is rounded.
Kilojoules to joules conversion table
| Kilojoules | Joules |
|---|---|
| 1 kJ | 1,000 J |
| 2 kJ | 2,000 J |
| 3 kJ | 3,000 J |
| 4 kJ | 4,000 J |
| 5 kJ | 5,000 J |
| 6 kJ | 6,000 J |
| 7 kJ | 7,000 J |
| 8 kJ | 8,000 J |
| 9 kJ | 9,000 J |
| 10 kJ | 10,000 J |
| 12 kJ | 12,000 J |
| 15 kJ | 15,000 J |
| 20 kJ | 20,000 J |
| 25 kJ | 25,000 J |
| 50 kJ | 50,000 J |
| 100 kJ | 100,000 J |
| 200 kJ | 200,000 J |
| 300 kJ | 300,000 J |
| 500 kJ | 500,000 J |
| 1000 kJ | 1,000,000 J |
| 2000 kJ | 2,000,000 J |
| 5000 kJ | 5,000,000 J |
| 10000 kJ | 10,000,000 J |
What is a kilojoule?
A thousand joules. Food energy outside the US is labelled here, alongside or instead of calories.
What is a joule?
The SI unit: one newton acting through one metre. Dropping a small apple one metre releases about one joule.
How many joules are in a kilojoule?
One kilojoule is 1000 joules, exactly. Going the other way, one joule is 0.001 kilojoules. Both figures come from the same defined relation rather than from a measurement, which is why they are the same today as they were in 1959.
Every energy unit here
| Unit | Symbol | One of these is |
|---|---|---|
| Joules | J | the base unit |
| Kilojoules | kJ | 1000 joule |
| Calories | cal | 4.184 joule |
| Kilocalories | kcal | 4184 joule |
| Watt-hours | Wh | 3600 joule |
| Kilowatt-hours | kWh | 3600000 joule |
| British thermal units | BTU | 1055.0559 joule |
| Foot-pounds | ft·lbf | 1.3558179 joule |
Source: NIST Special Publication 811 — the thermochemical calorie is exactly 4.184 J
Questions people actually ask
- How many joules are in a kilojoule?
- 1000. The SI unit: one newton acting through one metre. Dropping a small apple one metre releases about one joule.
- How do I convert joules back to kilojoules?
- Divide by 1000, or multiply by 0.001 — they are the same operation.
Other energy conversions
Joules to kilojoules — the same conversion the other way.