Where each energy unit is used
- Joule (J) and kilojoule (kJ) are the SI units. Food labels in Europe and Australia show kJ next to kcal.
- Kilocalorie (kcal) is the food Calorie with a capital C. A snack with 200 Calories has 200 kcal, or about 837 kJ.
- Kilowatt-hour (kWh) is how electricity is billed. A 1,000 W heater running for one hour uses 1 kWh.
- British thermal unit (BTU) rates heaters and air conditioners in the US. 1 kWh is about 3,412 BTU.
- Electronvolt (eV) is used in physics for the energy of single particles.
This converter uses the thermochemical calorie of exactly 4.184 joules, which is what food labels are based on. The international table calorie of 4.1868 J differs by less than 0.1 percent.
Common energy conversions
| From | Equals |
|---|---|
| 1 kilocalorie | 4.184 kilojoules |
| 1 kilojoule | 0.2390057361 kilocalories |
| 1 kilowatt-hour | 3,412.141633 British thermal units |
| 1 kilowatt-hour | 3,600,000 joules |
| 1 British thermal unit | 1.055055853 kilojoules |
| 1 watt-hour | 3,600 joules |
| 1 calorie | 4.184 joules |
Food energy: kcal to kJ
| Kilocalories (kcal) | Kilojoules (kJ) |
|---|---|
| 50 | 209.2 |
| 100 | 418.4 |
| 150 | 627.6 |
| 200 | 836.8 |
| 250 | 1,046 |
| 300 | 1,255.2 |
| 400 | 1,673.6 |
| 500 | 2,092 |
| 1,000 | 4,184 |
| 1,500 | 6,276 |
| 2,000 | 8,368 |
| 2,500 | 10,460 |
How to use it
- 1Pick the unit you have on the left and the unit you want on the right.
- 2Type a value on either side. The other side updates as you type, and the swap button turns the conversion around.
- 3Read the result and the factor below it, or tap any unit in the list to convert into it. Copy the result or a link to share it.
Frequently asked questions
How many kJ are in a kcal?
Exactly 4.184. A daily intake of 2,000 kcal is 8,368 kJ.
What is the difference between a calorie and a Calorie?
The Calorie on food labels, with a capital C, is a kilocalorie: 1,000 small calories. Most people mean kcal when they say calories.
How many BTU are in a kWh?
About 3,412 BTU. A 12,000 BTU per hour air conditioner moves about 3.5 kW of heat.
What does 1 kWh of electricity mean?
It is the energy a 1,000 watt device uses in one hour, or 3.6 million joules.