Energy Converter
Convert energy between joules, calories, watt-hours, kWh, and BTU.
How to use the energy converter
Enter a value, pick the unit you have, and choose the unit you want. The result shows as you type, and the swap button flips the two units when you need the reverse.
It links the units that rarely line up by hand: joules and kilojoules for physics, calories and kilocalories for food, watt-hours and kWh for electricity, and BTU for heating and cooling.
Common energy conversions
| 1 kilowatt-hour | 3412.14 BTU |
| 1 kilowatt-hour | 3,600,000 joules |
| 1 kilocalorie | 4184 joules |
| 1 calorie | 4.184 joules |
| 1 BTU | 1055.06 joules |
| 1 kilojoule | 0.239006 kilocalories |
About energy units
The joule is the SI unit of energy. It is tiny next to daily figures, so larger units take over: the kilojoule for nutrition labels outside the US, the kilowatt-hour on your power bill, and the BTU on furnaces and air conditioners.
The food calorie is a frequent source of confusion. One food Calorie is really a kilocalorie, or 1,000 small calories. This tool lists both calorie and kilocalorie so you can pick the one your label uses.
Frequently asked questions
- How many BTU are in a kilowatt-hour?
- One kilowatt-hour is about 3412.14 BTU. That figure shows up on heating and cooling specs, where power is often rated in BTU but billed in kWh.
- Is a food calorie the same as a calorie here?
- No. A food Calorie is a kilocalorie, equal to 1,000 small calories. Pick kilocalorie to match nutrition labels, or calorie for the smaller scientific unit.
- How do I convert joules to calories?
- Divide joules by 4.184 to get small calories, or by 4184 to get kilocalories. So 4184 joules is 1 kilocalorie, the energy on a typical food label.
- What is a watt-hour?
- A watt-hour is the energy of one watt running for one hour, which is 3,600 joules. A kilowatt-hour is 1,000 of those, the standard unit on electricity bills.