Convert kilojoules to joules

1 kJ=1,000J

Use the converter below to change any kilojoules value into joules instantly — with formula, conversion table, and real-world examples.

You have

Equals

1,000

Conversion formula

Forward

joules = kilojoules × 1,000

Reverse

kilojoules = joules × 0.001

Example: 10 kJ × 1,000 = 10,000 J.

About both units

From

Kilojoule

The kilojoule equals 1000 joules. Used on European nutrition labels (required by EU law alongside kcal), for mechanical work specifications, and some engineering contexts. A 100 g chocolate bar contains about 2100 kJ.

Real-world: 100 g chocolate: ~2100 kJ. EU daily intake (adult): ~8400 kJ. Tesla Model 3 battery: ~270 MJ = 270,000 kJ.

Read full kilojoule reference →

Joule

The joule is the SI unit of energy, work and heat. Defined as one newton-metre or one watt-second. Named after James Prescott Joule who demonstrated the mechanical equivalent of heat. Lifting a 100 g apple 1 metre requires about 1 J.

Real-world: Lifting a 100 g apple 1 m: ≈ 1 J. 100 kcal snack: 418,400 J. Hand grenade: ~650 kJ.

Read full joule reference →

Kilojoule to Joule conversion table

Common kilojoules to joules values for quick reference.

Kilojoule (kJ)	Joule (J)
1 kJ	1,000 J
10 kJ	10,000 J
100 kJ	100,000 J
500 kJ	500,000 J
1,000 kJ	1,000,000 J
5,000 kJ	5,000,000 J
10,000 kJ	10,000,000 J
50,000 kJ	50,000,000 J
100,000 kJ	100,000,000 J
500,000 kJ	500,000,000 J

Tips & common mistakes

Quick tips

1 kJ = 1000 J = 0.239 kcal.
EU nutrition labels must show both kJ and kcal.
For quick conversion: kcal × 4.2 = kJ.

Avoid these

Assuming European labels use kcal only — they use both kJ and kcal.
Confusing kJ with kW (power).
Using kcal when kJ is requested in scientific context.

Frequently asked questions

How many joules in a kilojoule?

One kilojoule equals 1,000 joules.

How do I convert kilojoules to joules?

Multiply the kilojoule value by 1,000 to get the equivalent in joules.

What is 100 kilojoules in joules?

100 kilojoules equals 100,000 joules.

Is a kilojoule bigger than a joule?

Yes. 1 kilojoule equals 1,000 joules, so one kilojoule is larger.

How to convert kilojoules to joules without a calculator?

Multiply by 1,000 for a quick estimate; use a calculator for precise results.

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