⚡ Energy converter
Convert between joules, calories, kilocalories, kilowatt-hours and BTU. Enter a value and pick its unit to see it in every other unit.
Popular energy conversions
| Conversion | Rate |
|---|---|
| Kilocalories to calories | 1 kcal = 1,000 cal |
| Calories to kilocalories | 1 cal = 0.001 kcal |
| Kilojoules to kilocalories | 1 kJ = 0.23900574 kcal |
| Kilocalories to kilojoules | 1 kcal = 4.184 kJ |
| Kilowatt-hours to joules | 1 kWh = 3,600,000 J |
| Joules to calories | 1 J = 0.23900574 cal |
| British Thermal Units to kilowatt-hours | 1 BTU = 0.00029307107 kWh |
| Kilowatt-hours to British thermal units | 1 kWh = 3,412.1416 BTU |
About energy units
Food energy on US labels is in kilocalories, even though the label says "Calories". One kilocalorie is 4.184 kilojoules.
Electricity is billed by the kilowatt-hour, which is 3.6 million joules. Heating is often rated in BTU.
Energy units
| Unit | Symbol | In joules |
|---|---|---|
| Joule | J | 1 J |
| Kilojoule | kJ | 1,000 J |
| Megajoule | MJ | 1,000,000 J |
| Calorie | cal | 4.184 J |
| Kilocalorie | kcal | 4,184 J |
| Watt-hour | Wh | 3,600 J |
| Kilowatt-hour | kWh | 3,600,000 J |
| British Thermal Unit | BTU | 1,055.055853 J |
| Therm | thm | 105,505,585.3 J |
| Electronvolt | eV | 1.602176634 × 10⁻¹⁹ J |
All energy conversions
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From kilojoules
From megajoules
From calories
From kilocalories
From watt-hours
From kilowatt-hours
From British thermal units
From therms
Energy unit definitions
- Joule (J)
- The joule is the SI unit of energy: the work done by a force of one newton over one meter.
- Kilojoule (kJ)
- A kilojoule is 1,000 joules. Food labels in Australia and Europe give energy in kJ next to kcal.
- Megajoule (MJ)
- A megajoule is 1,000,000 joules, about the kinetic energy of a one-tonne car at 160 km/h.
- Calorie (cal)
- A small calorie (thermochemical) is exactly 4.184 joules, the energy to warm one gram of water by about one degree Celsius.
- Kilocalorie (kcal)
- A kilocalorie is 1,000 small calories. The "Calories" on US food labels are kilocalories.
- Watt-hour (Wh)
- A watt-hour is the energy of one watt for one hour, 3,600 joules. Batteries are rated in watt-hours.
- Kilowatt-hour (kWh)
- A kilowatt-hour is 1,000 watt-hours, or 3.6 million joules. Electricity bills charge by the kWh.
- British Thermal Unit (BTU)
- A British thermal unit (International Table) is about 1,055 joules, the heat that warms one pound of water by one degree Fahrenheit.
- Therm (thm)
- A therm is 100,000 BTU. US natural gas bills are often charged per therm.
- Electronvolt (eV)
- An electronvolt is the energy an electron gains across one volt, exactly 1.602176634 × 10⁻¹⁹ joules. Particle physics uses it.