Popular energy conversions
- Joules to kilojoules1 J = 0.001 kJ
- Joules to calories1 J = 0.239006 cal
- Joules to kilocalories1 J = 0.000239006 kcal
- Joules to kilowatt-hours1 J = 2.77778×10⁻⁷ kWh
- Joules to British thermal units1 J = 0.000947817 BTU
- Kilojoules to joules1 kJ = 1,000 J
- Kilojoules to calories1 kJ = 239.006 cal
- Kilojoules to kilocalories1 kJ = 0.239006 kcal
- Kilojoules to kilowatt-hours1 kJ = 0.000277778 kWh
- Kilojoules to British thermal units1 kJ = 0.947817 BTU
- Calories to joules1 cal = 4.184 J
- Calories to kilojoules1 cal = 0.004184 kJ
- Calories to kilocalories1 cal = 0.001 kcal
- Calories to kilowatt-hours1 cal = 0.00000116222 kWh
- Calories to British thermal units1 cal = 0.00396567 BTU
- Kilocalories to joules1 kcal = 4,184 J
- Kilocalories to kilojoules1 kcal = 4.184 kJ
- Kilocalories to calories1 kcal = 1,000 cal
- Kilocalories to kilowatt-hours1 kcal = 0.00116222 kWh
- Kilocalories to British thermal units1 kcal = 3.96567 BTU
- Kilowatt-hours to joules1 kWh = 3,600,000 J
- Kilowatt-hours to kilojoules1 kWh = 3,600 kJ
- Kilowatt-hours to calories1 kWh = 860,421 cal
- Kilowatt-hours to kilocalories1 kWh = 860.421 kcal
- Kilowatt-hours to British thermal units1 kWh = 3,412.14 BTU
- British thermal units to joules1 BTU = 1,055.06 J
- British thermal units to kilojoules1 BTU = 1.05506 kJ
- British thermal units to calories1 BTU = 252.164 cal
- British thermal units to kilocalories1 BTU = 0.252164 kcal
- British thermal units to kilowatt-hours1 BTU = 0.000293071 kWh
- Electronvolts to joules1 eV = 1.60218×10⁻¹⁹ J
- Joules to electronvolts1 J = 6.24151×10¹⁸ eV
- Therms to kilowatt-hours1 thm = 29.3001 kWh
- Kilowatt-hours to therms1 kWh = 0.0341296 thm
- Megajoules to kilowatt-hours1 MJ = 0.277778 kWh
- Kilowatt-hours to megajoules1 kWh = 3.6 MJ
- Watt-hours to joules1 Wh = 3,600 J
- Joules to watt-hours1 J = 0.000277778 Wh
- Foot-pounds to joules1 ft⋅lbf = 1.35582 J
- Joules to foot-pounds1 J = 0.737562 ft⋅lbf
About energy units
Energy appears in many guises — heat, work, food energy, electricity — and each field kept its own unit. The joule is the SI unit. A food “Calorie” is a kilocalorie (4,184 J using the thermochemical calorie); electricity is billed in kilowatt-hours (3.6 MJ); heating and cooling equipment is rated in BTU (about 1,055 J).
Energy unit reference
| Unit | Symbol | Value in J | System |
|---|---|---|---|
| Joule | J | 1 J | SI |
| Millijoule | mJ | 0.001 J | SI |
| Kilojoule | kJ | 1,000 J | SI |
| Megajoule | MJ | 1,000,000 J | SI |
| Gigajoule | GJ | 1,000,000,000 J | SI |
| Watt-hour | Wh | 3,600 J | Metric |
| Kilowatt-hour | kWh | 3,600,000 J | Metric |
| Megawatt-hour | MWh | 3,600,000,000 J | Metric |
| Gigawatt-hour | GWh | 3,600,000,000,000 J | Metric |
| Calorie (thermochemical) | cal | 4.184 J | Other |
| Kilocalorie (food Calorie) | kcal | 4,184 J | Other |
| Calorie (International Table) | cal_IT | 4.1868 J | Other |
| British thermal unit | BTU | 1,055.0559 J | US customary |
| Million BTU | MMBtu | 1,055,055,900 J | US customary |
| Therm (US) | thm | 105,480,400 J | US customary |
| Quad | quad | 1.0550559×10¹⁸ J | US customary |
| Electronvolt | eV | 1.6021766×10⁻¹⁹ J | Other |
| Kiloelectronvolt | keV | 1.6021766×10⁻¹⁶ J | Other |
| Megaelectronvolt | MeV | 1.6021766×10⁻¹³ J | Other |
| Erg | erg | 1×10⁻⁷ J | CGS |
| Foot-pound | ft⋅lbf | 1.3558179 J | US customary |
| Horsepower-hour | hp⋅h | 2,684,519.5 J | US customary |
| Ton of TNT | tTNT | 4,184,000,000 J | Other |
Frequently asked questions
What is the SI unit of energy?
This converter uses the joule (J) as its reference unit; every other unit is defined relative to it.
How many energy units can I convert?
23 units are supported here, across SI, Metric, Other, US customary, CGS systems. Every pair can be converted in both directions.
Does this energy converter work offline?
Yes. Once the page has loaded, every calculation runs locally in your browser — nothing is sent to a server.