Energy Converter
Convert between joules, kilowatt hours, calories, food Calories and BTU.
Processing: This tool runs entirely in your browser. Your input and any file you open stay on your device — nothing is uploaded to a server.
How to use the energy converter
- Type the amount you want to convert.
- Choose the unit you have and the unit you want.
- Read the result, or use the table showing all 8 units at once.
About this tool
The confusing one is the calorie. The 'Calorie' on a food label is a kilocalorie: 1,000 of the small calories used in physics. A 500-Calorie meal is 500 kcal, or about 2,092 kilojoules — which is why European labels showing kilojoules produce such large numbers.
Electricity is billed in kilowatt hours: one kilowatt drawn for one hour, or 3.6 million joules. BTU still appears on heating and air-conditioning equipment.
Common uses
- Converting a food label between Calories and kilojoules.
- Comparing an appliance's kWh rating against joules.
- Reading a heating output given in BTU.
Frequently asked questions
- Is a food Calorie the same as a calorie?
- No. The capital-C Calorie on labels is a kilocalorie — 1,000 small calories. Both are listed here separately.
- How many joules are in a kilowatt hour?
- 3,600,000. One watt is one joule per second, so a kilowatt for an hour is 1,000 × 3,600 joules.
Related tools
Power Converter
Convert between watts, kilowatts, mechanical and metric horsepower, and BTU per hour.
Data Storage Converter
Convert between bytes, kilobytes, megabytes, gigabytes and their binary equivalents.
Temperature Converter
Convert between Celsius, Fahrenheit and Kelvin with the formulas shown.
Pressure Converter
Convert between pascals, bar, psi, atmospheres, torr and mmHg.