Kilojoule (kJ)

Definition

One thousand joules — the metric food-energy unit used outside the US.

History

The kilojoule is one thousand joules, the metric unit of energy built on the SI joule. It is the food-energy unit preferred where the metric system is standard.

Where it is used

Kilojoules are used on nutrition labels outside the United States and throughout physics and engineering.

Typical uses include nutrition labels outside the US, physics.

Conversion pages

These pages convert kilojoule to or from another unit in energy.

• Kilocalorie to kilojoule

Other Energy units

• Kilocalorie (kcal)
• Calorie (cal)
• Joule (J)
• Kilowatt-hour (kWh)
• British thermal unit (BTU)
• Watt-hour (Wh)

Sources

• NIST SP 811 NIST SP 811, Appendix B; ISO 80000-5 (energy) · Dataset reviewed Nov 11, 2026