Energy Converter
Enter an energy value and choose your source and target units to convert instantly between joules, kilojoules, calories, kilocalories, kilowatt-hours, and BTU.
How the Energy Converter formula works
Every unit routes through joules as a common base:
value_in_joules = value × factor_of_source_unit result = value_in_joules / factor_of_target_unit
For example, 1 calorie = 4.184 joules and 1 kWh = 3,600,000 joules.
Step-by-step calculation
- Multiply the entered value by its unit's conversion factor to get joules.
- Divide that value by the target unit's conversion factor.
- Round to a sensible number of decimal places.
Worked example
Converting 2,000 kilocalories (a common daily food energy figure) to kilojoules: 2,000 × 4.184 = 8,368 kJ.
Frequently asked questions
Why does food energy use 'Calories' with a capital C?
A food 'Calorie' (capital C) is actually a kilocalorie (1,000 small calories) — a naming convention that causes frequent confusion, since the scientific 'calorie' is a much smaller unit.
What's a BTU used for?
A British Thermal Unit (BTU) is commonly used to rate heating and cooling equipment, like air conditioners and furnaces, describing how much heat energy they can move or generate per hour.