Convert Kilojoule to Joule (kJ → J)
The kilojoule is the standard unit on European nutrition labels and in mid-scale chemical and physical calculations.
Kilojoule to Joule Conversion Table
10 common values| Kilojoule | Joule |
|---|---|
| 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 |
How to Convert Kilojoule to Joule Manually
Step by StepConverting kilojoules to joules is straightforward: multiply by the conversion factor. Follow these three steps to do it by hand or in your head.
- 1Take your value in kilojoulesStart with the number of kilojoules (kJ) you want to convert.
- 2Multiply by 1,000The conversion factor from kJ to J is 1,000. Multiply your value by this number.
- 3Read the result in joulesThe result is your value in joules (J).
Formula
Multiply the value in kilojoules by 1,000. For the reverse direction, multiply by 0.001.
J = kJ × 1,000kJ = J × 0.001Tips
Use these in everyday conversions- 1 kJ = 1000 J = 0.239 kcal.
- EU nutrition labels must show both kJ and kcal.
- For quick conversion: kcal × 4.2 = kJ.
Common Mistakes
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.
About Kilojoule and Joule
What is the Kilojoule?
The kilojoule equals 1,000 joules and is the standard unit on European nutrition labels and in mid-scale chemical and physical calculations. EU regulations require food packaging to display energy in kilojoules (typically with kilocalories also shown for consumer familiarity): a chocolate bar might show '2,100 kJ / 500 kcal' per 100 g. The kilojoule is also common in chemistry (bond energies), electrical engineering (capacitor storage), and small-mechanical-energy contexts. A car battery typically stores about 1,800 kJ; lifting a person 1 meter requires roughly 0.7 kJ. The kilojoule relates to the joule (1,000 J = 1 kJ), the kilocalorie (1 kcal = 4.184 kJ), the watt-hour (1 kWh = 3,600 kJ), and the megajoule (1,000 kJ = 1 MJ). The conversion factor 4.184 (kJ per kcal) is one of the most-used numbers in nutrition labeling.
- EU and UK nutrition labels
- Mechanical work in engineering
- Battery capacity in vehicles
100 g chocolate: ~2100 kJ. EU daily intake (adult): ~8400 kJ. Tesla Model 3 battery: ~270 MJ = 270,000 kJ.
What is the Joule?
The joule is the SI unit of energy, work, and heat, named after English physicist James Prescott Joule (1818–1889). Defined as the energy transferred when a force of one newton acts over a distance of one meter (1 J = 1 N·m), the joule unifies mechanical work, electrical energy (1 J = 1 watt-second = 1 V·C), and thermal energy. A typical apple has about 250,000 joules of chemical energy when metabolized, lifting an apple 1 meter requires roughly 1 joule of mechanical work, and a single joule could light a 1-watt LED for one second. The joule is fundamental in physics, mechanical engineering, electrical engineering, and nutrition (European food labels show kilojoules). It relates to the kilojoule (1 kJ = 1,000 J), the calorie (1 cal = 4.184 J), the watt-hour (1 Wh = 3,600 J), and the BTU (1 BTU ≈ 1,055 J). Modern definitions of the kilogram and the Kelvin both reference the joule.
- Physics and engineering calculations
- Scientific nutrition measurement (European labels)
- Impact energy in engineering (Charpy test)
Lifting a 100 g apple 1 m: ≈ 1 J. 100 kcal snack: 418,400 J. Hand grenade: ~650 kJ.