Energy Converter
Convert energy units: J, kJ, cal, kWh, BTU, and more
Result
0.001
1 Joules (J) = 0.001 Kilojoules (kJ)
What energy measures
Energy is the capacity to do work. The SI unit is the joule (J), equal to one newton metre or one watt second.
Main units and where they are used
- Joule and kilojoule (kJ) – physics and food labels.
- Kilocalorie (kcal, 4184 J) – the energy value of food.
- Kilowatt hour (kWh, 3.6 MJ) – electricity bills.
- Electronvolt (eV) – atomic and particle physics; BTU (about 1055 J) – heating and cooling equipment in the USA.
Common pitfalls
kW and kWh are often confused: kW is power (how fast energy is used) while kWh is energy (how much was used). A 2 kW heater running for 3 hours uses 6 kWh. On food packaging calories normally mean kilocalories: 100 kcal = 418.4 kJ. The small calorie (4.184 J) and the kilocalorie must not be mixed up, since they differ by a factor of 1000.