Energy Converter
Convert energy between calories, kilocalories, joules, kilojoules, kilowatt-hours, BTU and more.
Enter your numbers to see the result.
Calories, joules and kilowatt-hours
All energy units measure the same thing, so they convert with fixed factors. The SI unit is the joule.
| Unit | In joules |
|---|---|
| 1 calorie (small) | 4.184 J |
| 1 kilocalorie (food Calorie) | 4,184 J |
| 1 BTU | 1,055 J |
| 1 watt-hour | 3,600 J |
| 1 kilowatt-hour | 3,600,000 J |
Food Calories vs calories
The "Calories" on US nutrition labels are kilocalories. A 2,000-Calorie diet is 2,000 kcal, or about 8,368 kJ. Labels in Europe and Australia show both kcal and kJ.
Everyday comparisons
- 1 kWh of electricity is about 860 kcal, roughly the energy in two large meals.
- Heating systems and air conditioners are rated in BTU; 1 kWh is about 3,412 BTU.
- A gallon of gasoline contains roughly 33.7 kWh of energy, the figure the EPA uses for MPGe ratings.
Frequently asked questions
How many kJ are in a calorie?
One food Calorie (kcal) equals 4.184 kilojoules.
How many BTU are in a kWh?
About 3,412 BTU.
Is a Calorie the same as a kilocalorie?
Yes. A capital-C Calorie on food labels is one kilocalorie, 1,000 small calories.
Last reviewed October 2026. Results are estimates; check important decisions with a qualified professional.