Convert between joules, calories, kilowatt-hours, BTUs and more in one step. Enter a value, pick your units, and see the result across every common energy unit instantly.
| Joule (J) | |
| Kilojoule (kJ) | |
| Calorie (cal) | |
| Kilocalorie (kcal) | |
| Watt-hour (Wh) | |
| Kilowatt-hour (kWh) | |
| British thermal unit (BTU) | |
| Electronvolt (eV) | |
| Foot-pound (ft·lb) |
How to Use
- Enter the energy value you want to convert.
- Choose the unit you are converting from.
- Choose the unit you want to convert to, or press Swap to reverse the direction.
- Press Convert — the result appears above, with every other unit listed in the table.
Key Features
- Nine energy units — joules, kilojoules, calories, kilocalories, watt-hours, kilowatt-hours, BTUs, electronvolts and foot-pounds.
- Live results — the conversion updates as you type, with a full comparison table.
- One-click swap — reverse the conversion direction instantly.
- 100% private — runs entirely in your browser; nothing is sent or stored.
FAQs
What is a BTU?
A British thermal unit is the energy needed to raise one pound of water by one degree Fahrenheit. One BTU equals about 1055.06 joules, and BTUs are often used for heating and cooling ratings.
What is the difference between a calorie and a kilocalorie?
One kilocalorie equals 1000 small calories. Food energy is measured in kilocalories, usually written as Calories with a capital C on nutrition labels.
How many joules are in a kilowatt-hour?
Exactly 3,600,000 joules. The kilowatt-hour is the unit your electricity bill uses, so this conversion is handy for working out energy costs.
Is my data sent anywhere?
No. Everything runs entirely in your browser and never transmits or saves your entries.
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