Energy Converter
1 J = 0.001 kJ
About the energy category
Energy: electricity bills, food calories, heating, and batteries.
You will reach for these conversions when understanding electricity bills (kWh) versus heater labels (BTU), or comparing food energy: calories vs kilojoules on imported packaging.
- One kWh runs a 2,000 W heater for 30 minutes
- A typical daily food intake: 2,000 kcal, about 8,370 kJ
Popular energy conversions
Common mistakes
- Calorie (food) vs calorie (physics): food labels mean kilocalories, a factor of 1,000
- Power (kW) vs energy (kWh): a 5 kW heater running 2 hours uses 10 kWh
Frequently asked questions
Which energy units does this converter support?
8 units: Joule, Kilojoule, Calorie, Kilocalorie, Watt-hour, Kilowatt-hour, and more. All conversions run locally in your browser, nothing is sent to a server.
How accurate are the energy conversions?
All factors follow the official SI definitions and internationally agreed standards. Results are shown with up to 8 significant digits, which is far beyond the precision of everyday measurements.
Is this converter free?
Yes, completely free and unlimited, supported by ads. No app install, no sign-up.