Free online energy converter
Energy is measured by field — joules in physics, kilocalories in nutrition, kilowatt-hours on your electricity bill, BTU in heating. This converter handles all of them.
Result
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All units
How to use
- Enter the energy value you want to convert.
- Select the unit you are converting from.
- Select the unit you want the result in.
- The converted value appears instantly, and the table below shows equivalents in all supported units.
Conversion reference
| From | To | Multiply by |
|---|---|---|
| kWh | Joules | 3,600,000 |
| kWh | kJ | 3,600 |
| kWh | BTU | 3,412.14 |
| kcal | Joules | 4,184 |
| kcal | kJ | 4.184 |
| BTU | Joules | 1,055.06 |
| BTU | kWh | 0.000293071 |
| cal | Joules | 4.184 |
Note: calories here are thermochemical calories (cal = 4.184 J exactly). Food/nutrition calories are kilocalories (kcal).
Energy in context
| Energy amount | Equivalent |
|---|---|
| 1 food calorie (kcal) | 4,184 joules |
| 1 kWh (electricity) | 3,600 kJ = 3,412 BTU |
| Typical household monthly use | ~900 kWh = 3,240 MJ |
| 1 BTU | Energy to raise 1 lb water by 1°F |
| Bolt of lightning | ~1 GJ (rough estimate) |
Notes
- Electronvolt conversions involve very large or very small numbers; the converter uses scientific notation for those values automatically.
- Calorie and kilocalorie values follow the thermochemical definition (1 cal = 4.184 J) used in chemistry and physics, not the international table calorie (4.1868 J).
- Results are rounded to 6 significant figures.
Frequently asked
How many joules are in a kilowatt-hour?
1 kilowatt-hour = 3,600,000 joules (3.6 megajoules). A kilowatt-hour is the energy used by a 1,000-watt device running for one hour.
What is the difference between a calorie and a kilocalorie?
A small calorie (cal) is the energy needed to raise 1 gram of water by 1°C. A kilocalorie (kcal) is 1,000 small calories. Food calories listed on nutrition labels are kilocalories — so 200 food calories = 200 kcal = 200,000 cal.
How do you convert BTU to kilowatt-hours?
1 BTU = 0.000293071 kWh. To convert kWh to BTU, multiply by 3,412.14. BTU (British Thermal Unit) is the heat needed to raise 1 pound of water by 1°F.
How many joules are in a kilocalorie?
1 kcal = 4,184 joules. This is the thermochemical definition used in nutrition.
What is an electronvolt?
An electronvolt (eV) is the energy gained by one electron moving through 1 volt of electric potential — about 1.602 × 10^-19 joules. It is used in atomic and particle physics.
How do I read my electricity bill in joules?
Multiply kilowatt-hours by 3,600,000. A typical US household uses about 900 kWh per month — roughly 3.24 × 10^9 joules (3.24 gigajoules).