Energy Converter
Convert energy units with the factor behind each answer. Energy is power over time, so kWh is a quantity of energy and kW is a rate.
1 kWh = 3.6 MJ
Common conversions
- 1 J = 2.777777778 × 10⁻⁷ kWh
- 1 kWh = 3,600,000 J
- 1 kWh = 3.6 MJ
- 1 Wh = 0.001 kWh
- 1 MWh = 1,000 kWh
- 1 kcal = 4.1868 kJ
- 1 BTU = 1.055055853 kJ
kW and kWh are different quantities
kW is power, a rate. kWh is energy: power multiplied by time. A 2 kW heater running for 3 hours uses 6 kWh. To go between them you need the time, which the kW to kWh calculator asks for.
Why 1 kWh is 3.6 million joules
One kilowatt is 1,000 joules per second, and one hour is 3,600 seconds, so 1 kWh = 1,000 × 3,600 J = 3,600,000 J = 3.6 MJ.
Thermal and particle units
kcal and BTU are used for heat, and eV for particle energies. The factors here are the International Table values.
Unit factors
Every unit in terms of the base unit shown. To convert, multiply by the factor of the unit you have and divide by the factor of the unit you want.
| Unit | Equals | What it is |
|---|---|---|
| µJ | 1 × 10⁻⁶ J | Microjoule. |
| mJ | 0.001 J | Millijoule. |
| J | 1 J | Joule, the SI unit of energy: one watt-second. |
| kJ | 1,000 J | Kilojoule. |
| MJ | 1,000,000 J | Megajoule. |
| kcal | 4,186.8 J | Kilocalorie (International Table), 4,186.8 J. Food and thermal energy. |
| BTU | 1,055.055853 J | British thermal unit (International Table). |
| Wh | 3,600 J | Watt-hour: one watt for one hour. |
| kWh | 3,600,000 J | Kilowatt-hour. The billing unit for electricity: one kilowatt for one hour. |
| MWh | 3,600,000,000 J | Megawatt-hour, for utility and plant energy. |
| eV | 1.602176634 × 10⁻¹⁹ J | Electron-volt: the energy of one electron through one volt. |
| keV | 1.602176634 × 10⁻¹⁶ J | Kiloelectron-volt. |
| MeV | 1.602176634 × 10⁻¹³ J | Megaelectron-volt. |
| cal | 4.1868 J | Calorie (International Table), 4.1868 J. The small calorie; a food Calorie is a kilocalorie. |
| GeV | 1.602176634 × 10⁻¹⁰ J | Gigaelectron-volt, a billion electron-volts. Particle accelerator energies. |
Conversion pages
J to kWhkWh to JWh to kWhkWh to WhJ to kJkJ to JkWh to BTUBTU to kWh
Frequently asked questions
What is the formula to convert kWh to MJ?
MJ = kWh × 3.6. For example, 2 kWh is 7.2 MJ.
How do I convert MJ back to kWh?
kWh = MJ × 0.2777777778. The Swap button above reverses the direction for any pair of units.
How do I convert kW to kWh?
Multiply the power in kW by the running time in hours. There is no fixed factor, because kW is a rate and kWh is an amount. The kW to kWh calculator does this for you.
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