Convert joules, watt-hours, calories and BTU

Engineers, students and energy specialists use it to compare values in joules, watt-hours, calories or BTU across different contexts.

Convert joules, watt-hours, calories and BTU. Everything runs in your browser, so the values you enter are never uploaded, shared, or stored.

How to use

Start by typing the numeric value you want to convert, with no unit and no extra text around it.
Give the source unit on the next line and the target unit on the last line, using the accepted abbreviations.
Run the conversion to get the equivalent expressed in the unit you chose.
Read the result again, checking the order of magnitude, before using it in a calculation or document.
Clear the fields when you want to start again with a different value.

Example

The sample converts an energy figure given in kilowatt-hours into joules. After converting, check that the magnitude makes sense: a kilowatt-hour is worth a great many joules, so the output should be a much larger number than the input you typed.

Input

500
kcal
kj

Output

500 kcal = 2092 kj

Limits and formats

Only the units listed by the tool are recognised; an abbreviation it does not expect will not convert.
Spelling and prefixes matter, so a unit typed with an unexpected capital letter may be rejected.
The arithmetic ignores appliance efficiency and losses; it converts a figure rather than measuring anything.
Re-read the result before putting it in an official document, since a unit slip is easy to make.

Where processing happens

The whole conversion is computed in the browser: the value and units you type stay on your device and are not sent anywhere. The tool applies the conversion factors and displays the equivalent.

Frequently asked questions

Which units can I use?

The tool recognises the abbreviations shown in the input area, covering joules and their multiples, watt-hours and kilowatt-hours, calories and kilocalories, and BTU. Copy one of those forms exactly to avoid a rejected entry.

Does the result account for energy losses?

No, the conversion is purely mathematical: it expresses one value in another unit. If you are assessing what an appliance really consumes, add efficiency or losses afterwards, based on the assumptions of your own study.

Can I convert between two similar metric units?

Yes, nothing forces you to cross between measurement systems. You can compare a kilowatt-hour with a joule, or a kilocalorie with a BTU, as long as both units appear among those the tool accepts.