kJ to Joules Converter
Convert kilojoule to joule instantly. 1 kJ = 1000 J, worked steps and a full reference table.
How to use it
- Type the value in kilojoule — the result updates as you type.
- Use Swap to flip the direction, or change either dropdown to convert between any two units.
- Click the result to copy it. The URL updates too, so you can bookmark or share the exact conversion.
Examples
| 1 kJ | 1000 J |
| 5 kJ | 5000 J |
| 10 kJ | 10000 J |
| 100 kJ | 100000 J |
One kilojoule equals 1000 joules (J). To convert kilojoules to joules, multiply by 1000; to go back the other way, multiply by 0.001 instead.
The converter above does it as you type and shows the working underneath, so you can check the arithmetic rather than take the number on trust.
What kilojoules and joules actually measure
Kilojoule (kJ) — A kilojoule is a thousand joules. Nutrition labels outside the US, and heating calculations.
Joule (J) — The joule is the SI unit of energy — one watt for one second. Physics, mechanical work and food energy in most of the world.
kJ to Joules conversion table
The most common values, worked out in advance. Anything not listed can be typed straight into the converter.
| kJ | J |
|---|---|
| 1 kJ | 1000 J |
| 2 kJ | 2000 J |
| 5 kJ | 5000 J |
| 10 kJ | 10000 J |
| 25 kJ | 25000 J |
| 50 kJ | 50000 J |
| 100 kJ | 100000 J |
How to convert kilojoules to joules by hand
Multiply the number of kilojoules by 1000.
For example, 25 kJ × 1000 = 25000 J.
Going the other way, divide by 1000 — or multiply by 0.001, which is the same thing and easier to do in your head.
Everything runs in your browser
There is no server involved in the calculation. The numbers you type never leave your device, nothing is logged, and the page keeps working with no connection once it has loaded. That is not a marketing line — it is simply how the tool is built, because a calculation like this has no reason to touch a network.
Questions people ask
How many J are in 1 kJ?
1 kJ equals exactly 1000 J. Multiply any value in kilojoule by 1000 to get joule.
Is anything uploaded to a server?
No. The whole calculation happens in your browser. Nothing is sent anywhere, and the page keeps working offline once loaded.
Last updated 18 August 2026