Energy Converter
Convert between joules, kilowatt-hours, calories, kilocalories, BTU and other energy units.
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Energy units
Every unit below converts to every other one in the calculator. Values are relative to the base unit, the joule (J).
| Unit | Symbol | System | Value |
|---|---|---|---|
| Joule | J | SI | Base unit |
| Kilojoule | kJ | SI | = 1000 J |
| Megajoule | MJ | SI | = 1000000 J |
| Watt-hour | Wh | SI-accepted | = 3600 J |
| Kilowatt-hour | kWh | SI-accepted | = 3600000 J |
| Calorie (thermochemical) | cal | metric | = 4.184 J |
| Kilocalorie (thermochemical) | kcal | metric | = 4184 J |
| British thermal unit (IT) | BTU | US customary | = 1055.05585262 J |
| Foot-pound-force | ft·lbf | US customary | = 1.3558179483314004 J |
| Electronvolt | eV | SI-accepted | = 1.602176634e-19 J |
| Erg | erg | CGS | = 1e-7 J |
Joule quick reference
| Joule | Kilojoule | Megajoule | Kilowatt-hour |
|---|---|---|---|
| 1 J | = 0.001 kJ | = 0.000001 MJ | ≈ 2.777777778e-7 kWh |
| 10 J | = 0.01 kJ | = 0.00001 MJ | ≈ 0.000002777777778 kWh |
| 100 J | = 0.1 kJ | = 0.0001 MJ | ≈ 0.00002777777778 kWh |
| 1000 J | = 1 kJ | = 0.001 MJ | ≈ 0.0002777777778 kWh |
Among the 11 energy units on this page, the smallest is the electronvolt (eV) and the largest is the kilowatt-hour (kWh).
More energy conversions
- Joule to Calorie (thermochemical)J → cal
- British thermal unit (IT) to KilojouleBTU → kJ
- Calorie (thermochemical) to Joulecal → J
- Kilowatt-hour to British thermal unit (IT)kWh → BTU
- Kilowatt-hour to MegajoulekWh → MJ
- British thermal unit (IT) to Kilowatt-hourBTU → kWh
- Foot-pound-force to Jouleft·lbf → J
- Kilojoule to British thermal unit (IT)kJ → BTU
- Megajoule to Kilowatt-hourMJ → kWh
- Joule to ElectronvoltJ → eV
- Joule to Foot-pound-forceJ → ft·lbf
- Electronvolt to JouleeV → J
About energy units
Energy and work share a unit: the joule, one newton acting over one meter. The kilowatt-hour on electricity bills is exactly 3.6 million joules.
There are several calories. This converter uses the thermochemical calorie (exactly 4.184 J), and the kilocalorie is the "Calorie" printed on food labels. The BTU here is the International Table BTU, exactly 1055.05585262 J.
Frequently asked questions
- Is a food Calorie the same as a calorie?
- No. A food Calorie (capital C) is a kilocalorie: 1000 calories, about 4.184 kJ.
- What is the difference between energy and power?
- Energy is an amount (joules, kWh). Power is the rate of using it (watts, horsepower). A 1 kW heater running for one hour uses 1 kWh of energy.
- How many kilojoules are in one joule?
- One joule = 0.001 kJ (kilojoules).
- How many megajoules are in one joule?
- One joule = 0.000001 MJ (megajoules).
- How many kilowatt-hours are in one joule?
- One joule ≈ 2.777777778e-7 kWh (kilowatt-hours).