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kJ
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What is a kilojoule?

The European nutrition-label energy unit — required alongside kcal

Definition

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.

Common uses

  • EU and UK nutrition labels
  • Mechanical work in engineering
  • Battery capacity in vehicles

🌍 Real-world scale

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

Convert from kilojoules

9 conversions
Kilojoule to Joule1 kJ = 1,000 JKilojoule to Megajoule1 kJ = 0.001 MJKilojoule to Kilowatt-Hour1 kJ = 0.0002778 kWhKilojoule to Watt-Hour1 kJ = 0.2778 WhKilojoule to Calorie1 kJ = 239.006 calKilojoule to Kilocalorie1 kJ = 0.239 kcalKilojoule to British Thermal Unit1 kJ = 0.9478 BTUKilojoule to Electronvolt1 kJ = 6.2415e21 eVKilojoule to Therm1 kJ = 9.4782e-6 thm

Convert to kilojoules

9 conversions
Joule to Kilojoule1 J = 0.001 kJMegajoule to Kilojoule1 MJ = 1,000 kJKilowatt-Hour to Kilojoule1 kWh = 3,600 kJWatt-Hour to Kilojoule1 Wh = 3.6 kJCalorie to Kilojoule1 cal = 0.004184 kJKilocalorie to Kilojoule1 kcal = 4.184 kJBritish Thermal Unit to Kilojoule1 BTU = 1.05506 kJElectronvolt to Kilojoule1 eV = 1.6022e-22 kJTherm to Kilojoule1 thm = 105,505.59 kJ

Tips

  • 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

  • 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.

FAQ about the kilojoule

What is a 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.
Where is the kilojoule used?
The kilojoule is commonly used for: EU and UK nutrition labels; Mechanical work in engineering; Battery capacity in vehicles.
What is an example of a kilojoule in real life?
100 g chocolate: ~2100 kJ. EU daily intake (adult): ~8400 kJ. Tesla Model 3 battery: ~270 MJ = 270,000 kJ.
What category does the kilojoule belong to?
The kilojoule is a unit of energy, part of the 10-unit energy category on UnitConv.
How accurate are kilojoule conversions?
All conversion factors follow NIST and BIPM international standards to 8 significant figures — the highest practical accuracy.
Explore all 10 energy units and their conversions.⚡ Energy hub →