How to use the energy converter
- Type a value in either box. Decimals with a comma or a point both work.
- Choose the units on each side, or press the arrows to swap them.
- The table below shows the value in every unit at once. Click a row to convert to that unit.
About energy units
The joule is the SI unit of energy. Food energy is usually given in kilocalories, and a food Calorie with a capital C is the same thing: 1 kcal is exactly 4.184 kJ. Labels in the EU and Australia give kilojoules, often next to kilocalories.
Electricity is billed in kilowatt-hours. One kWh is the energy of 1,000 watts running for an hour, exactly 3.6 MJ, or about 860 kcal. Heating and cooling in the US are rated in British thermal units, and 1 kWh is 3,412.14 BTU.
The classic mix-up is the calorie itself. A "calorie" on a food label is a kilocalorie, 1,000 of the small calories used in chemistry. A 2,000 kcal day is 8,368 kJ.
Popular energy conversions
Energy units
| Unit | Symbol | Definition |
|---|---|---|
| Joules | J | The base unit |
| Kilojoules | kJ | 1 kJ = 1,000 J |
| Megajoules | MJ | 1 MJ = 1,000,000 J |
| Calories | cal | 1 cal = 4.184 J |
| Kilocalories | kcal | 1 kcal = 4,184 J |
| Watt-hours | Wh | 1 Wh = 3,600 J |
| Kilowatt-hours | kWh | 1 kWh = 3,600,000 J |
| Megawatt-hours | MWh | 1 MWh = 3,600,000,000 J |
| British thermal units | BTU | 1 BTU = 1,055.055853 J |
| Electronvolts | eV | 1 eV = 1.602176634 × 10⁻¹⁹ J |
| Foot-pounds | ft·lbf | 1 ft·lbf = 1.355817948 J |
| Ergs | erg | 1 erg = 1 × 10⁻⁷ J |
Converting something else? The unit converter covers every kind of unit in one place.