Energy Converter
Convert between joules, calories, kilowatt-hours, BTU, electronvolts, and more energy units.
Energy Converter
Enter a value and select units to convert
1 J = 0.001 kJ
Common Values
| Joule | Kilojoule |
|---|---|
| 0.001 J | 1.0000e-6 kJ |
| 0.01 J | 1.0000e-5 kJ |
| 0.1 J | 0.0001 kJ |
| 1 J | 0.001 kJ |
| 2 J | 0.002 kJ |
| 5 J | 0.005 kJ |
| 10 J | 0.01 kJ |
| 25 J | 0.025 kJ |
| 50 J | 0.05 kJ |
| 100 J | 0.1 kJ |
| 1000 J | 1 kJ |
Available Units
Joule
J
Kilojoule
kJ
Calorie
cal
Kilocalorie
kcal
Watt-hour
Wh
Kilowatt-hour
kWh
BTU
BTU
Electronvolt
eV
Therm
therm
Foot-pound
ft·lbf
Related Converters
About Energy Conversion
The Energy Converter allows you to convert between 10 different units including Joule, Kilojoule, Calorie, Kilocalorie, Watt-hour, and 5 more.
Simply enter a value, select the source and target units, and get instant, accurate results. This converter is part of the Common converters category on FastConvert.
Whether you're a student, professional, or just need a quick conversion, FastConvert's Energy Converter delivers precise results in real-time. All calculations run directly in your browser — no data is sent to any server.
Frequently Asked Questions
How many calories are in a joule?
1 joule equals 0.2388 calories. Conversely, 1 calorie equals 4.184 joules.
What is a kilowatt-hour?
A kilowatt-hour (kWh) is a unit of energy equal to 3.6 million joules. It is the standard billing unit for electricity.
How do I convert kcal to kJ?
Multiply kilocalories by 4.184 to get kilojoules. Example: 2,000 kcal = 8,368 kJ.
What is a BTU?
BTU (British Thermal Unit) is the energy needed to raise 1 pound of water by 1°F. 1 BTU = 1,055 joules.
Is this energy converter free?
Yes, 100% free with no signup required.