Energy Converter
Convert between joules, calories, kWh, BTU, and more.
What is Energy?
An energy converter covering SI joules, food calories, electrical kWh, imperial BTUs, and physics units like eV.
How it works
Units are normalized to joules with standard definitions (1 cal = 4.184 J, 1 kWh = 3.6 MJ, etc.).
- Enter your input. Type or paste your input into the field above — the tool responds instantly.
- Review the result. Output updates live as you type. Everything runs entirely in your browser.
- Copy or download. Use the Copy button to grab the result, or Download to save it as a file.
Examples
Food vs electricity energy
Convert 1,000 calories to 4.184 megajoules — or switch between joules, watt-hours, BTUs, and therms for bills and engineering.
Common mistakes
Calories vs kilocalories
The calorie on food labels is actually a kilocalorie (1,000 cal). The converter is explicit about which unit is being used.
Frequently asked questions
Which units are supported?
Joules, kilojoules, calories, kilocalories, watt-hours, kilowatt-hours, BTUs, and therms.
What is the relationship between watts and joules?
A watt is a joule per second, so 1 kWh is exactly 3.6 million joules.
Is a food Calorie the same as a science calorie?
No — 1 food Calorie (capital C) equals 1,000 science calories. The converter keeps them distinct.