A kilocalorie (kcal) equals 1,000 small calories and is the unit behind the food "Calorie" shown on nutrition labels.
Kilocalories to Zettajoules
Convert Kilocalorie (kcal) to Zettajoule (ZJ) instantly with an exact formula, conversion table, and FAQ.
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Convert kilocalories (kcal) to zettajoules (ZJ) instantly with formula, conversion table, and FAQ.
Context values
Some unit families need one extra value for a physically accurate result.
A zettajoule (ZJ) is a metric-prefixed unit of energy equal to 1021 joules, using the SI zetta prefix.
ZJ = kcal × 4.184000000e-18
Results update instantly for Kilocalories to Zettajoules conversions.
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Formula
ZJ = kcal × 4.184000000e-18
kcal = ZJ × 2.390057361e+17
Conversion table
| 1 kcal | 4.184000e-18 ZJ |
| 5 kcal | 2.092000e-17 ZJ |
| 10 kcal | 4.184000e-17 ZJ |
| 20 kcal | 8.368000e-17 ZJ |
| 50 kcal | 2.092000e-16 ZJ |
| 100 kcal | 4.184000e-16 ZJ |
| 500 kcal | 2.092000e-15 ZJ |
| 1000 kcal | 4.184000e-15 ZJ |
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How the formula works
Both kilocalorie and zettajoule measure the same physical quantity, so converting between them is a single multiplication. Multiply a value in kilocalories by 4.184000000e-18 to get zettajoules. To reverse the conversion, multiply a zettajoule value by 2.390057361e+17 to get back to kilocalories.
Frequently asked questions
What is Kilocalorie (kcal)?
A kilocalorie (kcal) equals 1,000 small calories and is the unit behind the food "Calorie" shown on nutrition labels.
What is Zettajoule (ZJ)?
A zettajoule (ZJ) is a metric-prefixed unit of energy equal to 1021 joules, using the SI zetta prefix.
How do I convert kilocalories to zettajoules?
Multiply the kilocalorie value by 4.184000000e-18 to get the equivalent in zettajoules. For example, 5 kcal × 4.184000000e-18 = 2.092000e-17 ZJ.
Is this conversion exact?
Yes. Both units are defined against the SI base unit for this dimension, so the factor 4.184000000e-18 is an exact, non-rounded value.
Can I convert zettajoules back to kilocalories?
Yes. Divide the zettajoule value by 4.184000000e-18, or multiply it by 2.390057361e+17, to get kilocalories.
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About converting kilocalories to zettajoules
A kilocalorie (kcal) equals 1,000 small calories and is the unit behind the food "Calorie" shown on nutrition labels. A zettajoule (ZJ) is a metric-prefixed unit of energy equal to 1021 joules, using the SI zetta prefix.
Use this calculator to move between kilocalories and zettajoules accurately for homework, engineering, billing, or everyday energy calculations. The Universal Converter uses exact unit factors, so results stay consistent across the site.