A (small) calorie is a thermochemical unit of heat energy equal to 4.184 joules, historically the energy needed to raise 1 gram of water by 1°C.
Calories to Kilojoules
Convert Calorie (cal) to Kilojoule (kJ) instantly with an exact formula, conversion table, and FAQ.
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Convert calories (cal) to kilojoules (kJ) instantly with formula, conversion table, and FAQ.
Context values
Some unit families need one extra value for a physically accurate result.
A kilojoule (kJ) equals 1,000 joules and is commonly used on nutrition labels outside the United States.
kJ = cal × 0.004184
Results update instantly for Calories to Kilojoules conversions.
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Formula
kJ = cal × 0.004184
cal = kJ × 239.0057361
Conversion table
| 1 cal | 0.004184 kJ |
| 5 cal | 0.020920 kJ |
| 10 cal | 0.041840 kJ |
| 20 cal | 0.083680 kJ |
| 50 cal | 0.209200 kJ |
| 100 cal | 0.418400 kJ |
| 500 cal | 2.092000 kJ |
| 1000 cal | 4.184000 kJ |
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How the formula works
Both calorie and kilojoule measure the same physical quantity, so converting between them is a single multiplication. Multiply a value in calories by 0.004184 to get kilojoules. To reverse the conversion, multiply a kilojoule value by 239.0057361 to get back to calories.
Frequently asked questions
What is Calorie (cal)?
A (small) calorie is a thermochemical unit of heat energy equal to 4.184 joules, historically the energy needed to raise 1 gram of water by 1°C.
What is Kilojoule (kJ)?
A kilojoule (kJ) equals 1,000 joules and is commonly used on nutrition labels outside the United States.
How do I convert calories to kilojoules?
Multiply the calorie value by 0.004184 to get the equivalent in kilojoules. For example, 5 cal × 0.004184 = 0.020920 kJ.
Is this conversion exact?
Yes. Both units are defined against the SI base unit for this dimension, so the factor 0.004184 is an exact, non-rounded value.
Can I convert kilojoules back to calories?
Yes. Divide the kilojoule value by 0.004184, or multiply it by 239.0057361, to get calories.
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About converting calories to kilojoules
A (small) calorie is a thermochemical unit of heat energy equal to 4.184 joules, historically the energy needed to raise 1 gram of water by 1°C. A kilojoule (kJ) equals 1,000 joules and is commonly used on nutrition labels outside the United States.
Use this calculator to move between calories and kilojoules accurately for homework, engineering, billing, or everyday energy calculations. The Universal Converter uses exact unit factors, so results stay consistent across the site.