Quick reference table
Common energy conversions
| From | To |
|---|---|
| 1 kcal | 4.184 kJ |
| 1 kJ | 0.2390057361 kcal |
| 1 kWh | 3.6 MJ |
| 1 MJ | 0.2777777778 kWh |
| 1 BTU | 1.055055853 kJ |
| 1 kWh | 3,412.141633 BTU |
| 1 cal | 4.184 J |
| 1 Wh | 3,600 J |
How to convert energy
Energy appears as joules in physics, kilowatt-hours on electricity bills, calories and kilocalories in food, and BTU in heating and cooling. This tool converts between them all.
Every energy unit is a fixed multiple of one base unit, the J. To convert a value, multiply it by the size of the starting unit and divide by the size of the target unit. For example, to convert kcal to kJ, multiply by 4.184. To go the other way, divide by 4.184.
The converter above does this for you and shows the exact formula under the result.
Worked examples
Kilocalories (food Calories) to Kilojoules
| Kilocalories (food Calories) (kcal) | Kilojoules (kJ) |
|---|---|
| 1 kcal | 4.184 kJ |
| 2 kcal | 8.368 kJ |
| 5 kcal | 20.92 kJ |
| 10 kcal | 41.84 kJ |
| 25 kcal | 104.6 kJ |
| 50 kcal | 209.2 kJ |
| 100 kcal | 418.4 kJ |
| 1,000 kcal | 4,184 kJ |
Kilojoules to Kilocalories (food Calories)
| Kilojoules (kJ) | Kilocalories (food Calories) (kcal) |
|---|---|
| 1 kJ | 0.2390057361 kcal |
| 2 kJ | 0.4780114723 kcal |
| 5 kJ | 1.195028681 kcal |
| 10 kJ | 2.390057361 kcal |
| 25 kJ | 5.975143403 kcal |
| 50 kJ | 11.95028681 kcal |
| 100 kJ | 23.90057361 kcal |
| 1,000 kJ | 239.0057361 kcal |
Energy units explained
| Unit | Symbol | Equals |
|---|---|---|
| Joules | J | 1 J = 1 J |
| Kilojoules | kJ | 1 kJ = 1,000 J |
| Megajoules | MJ | 1 MJ = 1,000,000 J |
| Gigajoules | GJ | 1 GJ = 1,000,000,000 J |
| Watt-hours | Wh | 1 Wh = 3,600 J |
| Kilowatt-hours | kWh | 1 kWh = 3,600,000 J |
| Calories (thermochemical) | cal | 1 cal = 4.184 J |
| Kilocalories (food Calories) | kcal | 1 kcal = 4,184 J |
| BTU (IT) | BTU | 1 BTU = 1,055.05585262 J |
| Therms (US) | therm | 1 therm = 105,480,400 J |
| Foot-pounds | ft·lbf | 1 ft·lbf = 1.35581794833 J |
| Electronvolts | eV | 1 eV = 1.602177 × 10⁻¹⁹ J |
| Ergs | erg | 1 erg = 1 × 10⁻⁷ J |
| Horsepower-hours | hp·h | 1 hp·h = 2,684,519.53770 J |
Popular conversions: kwh to joules, calories to joules, kcal to kj, btu to kwh.
Frequently asked questions
How many kJ are in a kcal?
One kilocalorie (the 'Calorie' on food labels) is 4.184 kilojoules.
How many joules are in a kWh?
One kilowatt-hour is 3,600,000 joules, or 3.6 megajoules.
How do I convert kcal to kJ?
Multiply the value in kcal by 4.184 to get kJ. For example, 10 kcal = 41.84 kJ.
How many kJ is 1 kcal?
1 kcal = 4.184 kJ, and 1 kJ = 0.2390057361 kcal.
Does this energy converter work offline?
Yes. After the page has loaded once, all calculations run in your browser, so it keeps working without an internet connection.