Convert Joules to Kilojoules
Convert Joules to Kilojoules instantly. 1 Joule (J) equals 0.001 Kilojoules (kJ).
Joules to Kilojoules conversion table
| Joules (J) | Kilojoules (kJ) |
|---|---|
| 1 J | 0.001 kJ |
| 2 J | 0.002 kJ |
| 3 J | 0.003 kJ |
| 5 J | 0.005 kJ |
| 10 J | 0.01 kJ |
| 20 J | 0.02 kJ |
| 50 J | 0.05 kJ |
| 100 J | 0.1 kJ |
| 500 J | 0.5 kJ |
| 1,000 J | 1 kJ |
1 Joule = 0.001 Kilojoules · multiply Joules by 0.001
About converting Joules to Kilojoules
Joules (J) and Kilojoules (kJ) are both units of energy, so converting between them is a single multiplication: multiply your Joules figure by 0.001. Ten Joules comes to 0.01 Kilojoules, and a hundred works out at 0.1 Kilojoules.
Rule of thumb: going from Joules to Kilojoules divides, so the figure always shrinks — it takes about 1,000 Joules to make a single Kilojoule. If your answer came out bigger, you have the conversion the wrong way round.
What is a Joule?
The joule is the SI unit of energy and the reference every other energy unit here is defined against. One joule is one newton acting over one metre — push with a newton of force, move a metre, and you have spent a joule. It is named after James Prescott Joule, whose painstaking experiments established that heat and mechanical work are the same thing, measurable in the same units. That result sounds obvious now and was foundational then: it collapsed heat, motion and work into a single quantity called energy, which is why one unit can serve food, electricity, explosives and engines alike.
What is a Kilojoule?
A kilojoule is a thousand joules, the size at which the joule becomes practical for everyday quantities. In Australia and New Zealand it is the primary unit on nutrition labels — food energy is quoted in kilojoules first, with calories relegated to a secondary figure or dropped entirely — so shoppers there think about daily intake in thousands of kilojoules rather than thousands of calories. It is also the working unit of chemistry, where reaction and bond energies are tabulated per mole. European labels print both kJ and kcal, which is why the same packet carries two different numbers for the same food.
To put both in perspective: lifting an apple one metre takes about a joule, while a slice of bread carries roughly 300 kilojoules.
The converter above updates as you type, and the table lists common values for quick reference. Need the opposite direction? Use the Kilojoules to Joules converter, or browse all Energy converters.
Frequently asked questions
How many Kilojoules are in one Joule?
There are 0.001 Kilojoules in one Joule.
How do I convert Joules to Kilojoules?
Multiply the number of Joules by 0.001. For example, 10 Joules = 0.01 Kilojoules.
What is 100 Joules in Kilojoules?
100 Joules is equal to 0.1 Kilojoules.
How do I convert Kilojoules to Joules?
Multiply the Kilojoules value by 1,000 (or divide by 0.001).
Is this Joules to Kilojoules conversion exact?
Yes, exactly. Both units are fixed against the same base by definition, and 1 Joule = 0.001 Kilojoules is the complete value — nothing is rounded away.
What is a Joule?
The joule is the SI unit of energy and the reference every other energy unit here is defined against. One joule is one newton acting over one metre — push with a newton of force, move a metre, and you have spent a joule. It is named after James Prescott Joule, whose painstaking experiments established that heat and mechanical work are the same thing, measurable in the same units. That result sounds obvious now and was foundational then: it collapsed heat, motion and work into a single quantity called energy, which is why one unit can serve food, electricity, explosives and engines alike.
What is a Kilojoule?
A kilojoule is a thousand joules, the size at which the joule becomes practical for everyday quantities. In Australia and New Zealand it is the primary unit on nutrition labels — food energy is quoted in kilojoules first, with calories relegated to a secondary figure or dropped entirely — so shoppers there think about daily intake in thousands of kilojoules rather than thousands of calories. It is also the working unit of chemistry, where reaction and bond energies are tabulated per mole. European labels print both kJ and kcal, which is why the same packet carries two different numbers for the same food.