A zettajoule (ZJ) is a metric-prefixed unit of energy equal to 1021 joules, using the SI zetta prefix.
Zettajoules to Calories
Convert Zettajoule (ZJ) to Calorie (cal) instantly with an exact formula, conversion table, and FAQ.
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Convert zettajoules (ZJ) to calories (cal) instantly with formula, conversion table, and FAQ.
Context values
Some unit families need one extra value for a physically accurate result.
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.
cal = ZJ × 2.390057361e+20
Results update instantly for Zettajoules to Calories conversions.
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Formula
cal = ZJ × 2.390057361e+20
ZJ = cal × 4.184000000e-21
Conversion table
| 1 ZJ | 2.390057e+20 cal |
| 5 ZJ | 1.195029e+21 cal |
| 10 ZJ | 2.390057e+21 cal |
| 20 ZJ | 4.780115e+21 cal |
| 50 ZJ | 1.195029e+22 cal |
| 100 ZJ | 2.390057e+22 cal |
| 500 ZJ | 1.195029e+23 cal |
| 1000 ZJ | 2.390057e+23 cal |
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How the formula works
Both zettajoule and calorie measure the same physical quantity, so converting between them is a single multiplication. Multiply a value in zettajoules by 2.390057361e+20 to get calories. To reverse the conversion, multiply a calorie value by 4.184000000e-21 to get back to zettajoules.
Frequently asked questions
What is Zettajoule (ZJ)?
A zettajoule (ZJ) is a metric-prefixed unit of energy equal to 1021 joules, using the SI zetta prefix.
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.
How do I convert zettajoules to calories?
Multiply the zettajoule value by 2.390057361e+20 to get the equivalent in calories. For example, 5 ZJ × 2.390057361e+20 = 1.195029e+21 cal.
Is this conversion exact?
Yes. Both units are defined against the SI base unit for this dimension, so the factor 2.390057361e+20 is an exact, non-rounded value.
Can I convert calories back to zettajoules?
Yes. Divide the calorie value by 2.390057361e+20, or multiply it by 4.184000000e-21, to get zettajoules.
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About converting zettajoules to calories
A zettajoule (ZJ) is a metric-prefixed unit of energy equal to 1021 joules, using the SI zetta prefix. 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.
Use this calculator to move between zettajoules and calories accurately for homework, engineering, billing, or everyday energy calculations. The Universal Converter uses exact unit factors, so results stay consistent across the site.