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 Zeptojoules
Convert Calorie (cal) to Zeptojoule (zJ) instantly with an exact formula, conversion table, and FAQ.
Reserved for a responsive leaderboard above the conversion details.
Professional calculator style
World-scale conversion engine
30+ categories
6,500+ units
Instant results
Offline ready
Energy calculator
Energy Converter
Convert calories (cal) to zeptojoules (zJ) instantly with formula, conversion table, and FAQ.
Context values
Some unit families need one extra value for a physically accurate result.
A zeptojoule (zJ) is a metric-prefixed unit of energy equal to 10-21 joules, a fraction of a single joule, using the SI zepto prefix.
zJ = cal × 4.184000000e+21
Results update instantly for Calories to Zeptojoules conversions.
Reserved above the conversion cards and below the converter.
Formula
zJ = cal × 4.184000000e+21
cal = zJ × 2.390057361e-22
Conversion table
| 1 cal | 4.184000e+21 zJ |
| 5 cal | 2.092000e+22 zJ |
| 10 cal | 4.184000e+22 zJ |
| 20 cal | 8.368000e+22 zJ |
| 50 cal | 2.092000e+23 zJ |
| 100 cal | 4.184000e+23 zJ |
| 500 cal | 2.092000e+24 zJ |
| 1000 cal | 4.184000e+24 zJ |
Related conversions
Reserved between the cards and the FAQ so the page stays balanced.
How the formula works
Both calorie and zeptojoule measure the same physical quantity, so converting between them is a single multiplication. Multiply a value in calories by 4.184000000e+21 to get zeptojoules. To reverse the conversion, multiply a zeptojoule value by 2.390057361e-22 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 Zeptojoule (zJ)?
A zeptojoule (zJ) is a metric-prefixed unit of energy equal to 10-21 joules, a fraction of a single joule, using the SI zepto prefix.
How do I convert calories to zeptojoules?
Multiply the calorie value by 4.184000000e+21 to get the equivalent in zeptojoules. For example, 5 cal × 4.184000000e+21 = 2.092000e+22 zJ.
Is this conversion exact?
Yes. Both units are defined against the SI base unit for this dimension, so the factor 4.184000000e+21 is an exact, non-rounded value.
Can I convert zeptojoules back to calories?
Yes. Divide the zeptojoule value by 4.184000000e+21, or multiply it by 2.390057361e-22, to get calories.
Reserved between the FAQ and the article so the page stays balanced.
About converting calories to zeptojoules
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 zeptojoule (zJ) is a metric-prefixed unit of energy equal to 10-21 joules, a fraction of a single joule, using the SI zepto prefix.
Use this calculator to move between calories and zeptojoules accurately for homework, engineering, billing, or everyday energy calculations. The Universal Converter uses exact unit factors, so results stay consistent across the site.