Energy Converter
Converts energy between electrical, thermal, food and mechanical units. One kilowatt hour — the unit on your electricity bill — is 3.6 million joules, which is why kWh exists at all: joules are inconveniently small for household amounts.
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The formula
result = value × (from factor ÷ to factor)
Each energy unit is defined by its size relative to the joule, so converting between any two is a single multiplication.
Every energy unit
| Unit | Symbol | In one joule |
|---|---|---|
| joule | J | 1 |
| kilojoule | kJ | 0.001 |
| calorie | cal | 0.23900574 |
| kilocalorie | kcal | 0.00023900574 |
| watt hour | Wh | 0.00027777778 |
| kilowatt hour | kWh | 0.00000027777778 |
| British thermal unit | BTU | 0.00094781712 |
| foot-pound | ft·lb | 0.73756215 |
Frequently Asked Questions
How many joules are in a kilowatt hour?
Exactly 3,600,000. One watt is one joule per second, so a kilowatt for an hour is 1,000 × 3,600 J.
Are food calories the same as calories?
No. A food "Calorie" is a kilocalorie — 1,000 small calories, or 4,184 joules. Both are listed separately here to avoid the confusion.
What is a BTU?
The energy to raise one pound of water by one degree Fahrenheit — 1,055.06 joules. It is still standard for heating and air-conditioning capacity.