Convert calories to kilojoules
Converting calories to kilojoules is a common energy task, whether you are checking a recipe, a spec sheet, a travel distance or a homework problem. Since 1 cal equals 0.004184 kJ, the math is a single multiplication — and this page does it for you instantly, with the formula, a table of common values and answers to the questions people ask most.
Exact factor
How to convert calories to kilojoules
To convert calories to kilojoules, multiply the number of calories by 0.004184. For example, 10 cal × 0.004184 = 0.04184 kJ.
kJ = cal × 0.004184
- Write down the value in calories you want to convert.
- Multiply it by 0.004184 (the exact cal→kJ factor).
- The result is your value in kilojoules. Check it below with the converter or the table.
Conversion table
Common values of calories and their equivalents in kilojoules:
| cal | kJ |
|---|---|
| 1 | 0.004184 |
| 2 | 0.008368 |
| 3 | 0.012552 |
| 4 | 0.016736 |
| 5 | 0.02092 |
| 10 | 0.04184 |
| 20 | 0.08368 |
| 25 | 0.1046 |
| 50 | 0.2092 |
| 100 | 0.4184 |
| 250 | 1.046 |
| 500 | 2.092 |
About these units
Calorie (cal). The small calorie is the energy needed to raise one gram of water by 1 °C, defined as exactly 4.184 joules. It is mostly used in chemistry and heat calculations.
Kilojoule (kJ). A kilojoule is 1,000 joules, the practical unit for food energy in Australia and Europe and for mechanical work. One kilocalorie equals 4.184 kilojoules.
Frequently asked questions
How do I convert calories to kilojoules?
To convert calories to kilojoules, multiply the number of calories by 0.004184. For example, 10 cal × 0.004184 = 0.04184 kJ. Or skip the math: type the value into the converter at the top of this page and the result updates instantly.
How many kilojoules are in 1 calorie?
1 cal = 0.004184 kJ. That is the fixed relationship used by this converter and by international standards.
How many calories are in 1 kilojoule?
1 kJ = 239.006 cal. If you are converting in the opposite direction, use our Kilojoule to Calorie converter for the dedicated table and FAQ.
Is the calories to kilojoules conversion exact?
Yes. Both units are defined by international agreement, so the factor of 0.004184 is exact. Displayed results are rounded to 6 significant digits only for readability.
What is calorie used for?
The small calorie is the energy needed to raise one gram of water by 1 °C, defined as exactly 4.184 joules. It is mostly used in chemistry and heat calculations.