Free Energy Converter
Convert joules, kilojoules, calories, kilowatt-hours and BTU.
Choose a value and the units and the result shows at once. It uses exact definitions such as 1 kWh = 3.6 million joules and 1 thermochemical calorie = 4.184 J.
How to use the Energy Converter
- Enter your values, choosing the units you are working in.
- Read the result and the supporting numbers shown beneath it.
- Check the result against a second method or a reference table before you rely on it.
About the Energy Converter
Convert joules, kilojoules, calories, kilowatt-hours and BTU.
Quick, reliable engineering arithmetic saves time on site and in the workshop. These tools show their working so you can check the result.
Getting started with the Energy Converter
Using the energy converter takes a minute or two. Your entries are saved in this browser, so you can come back later and carry on.
Tips for better results
Food calories on labels are kilocalories, so 1 Calorie on a label is 1,000 calories, or 4.184 kJ.
Keep units consistent from start to finish.
These tools are for estimates. Safety critical designs need a qualified engineer.
Privacy and where your data goes
Everything you type into the energy converter stays on your own device. Zapxa does not receive your numbers or documents. If you clear your browser data, your saved entries will be removed, so download a PDF of anything you want to keep.
Frequently asked questions
How many joules are in a kilowatt-hour?
Exactly 3,600,000 joules.
Is a food Calorie the same as a calorie?
No. A food Calorie is a kilocalorie, which is 1,000 small calories.
Is the energy converter free?
Yes. It is free to use with no signup, no watermark and no usage limits.
Is my data private?
Yes. Your inputs are processed in your browser and saved only in its local storage. They are not uploaded to our servers.
Does it work on mobile?
Yes. Zapxa works on phones, tablets and desktops. Use the print button or download a PDF to keep a copy.
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