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.
Zeptojoules to Kilojoules
Convert Zeptojoule (zJ) to Kilojoule (kJ) 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 zeptojoules (zJ) 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 = zJ × 1.000000000e-24
Results update instantly for Zeptojoules to Kilojoules conversions.
Reserved above the conversion cards and below the converter.
Formula
kJ = zJ × 1.000000000e-24
zJ = kJ × 1.000000000e+24
Conversion table
| 1 zJ | 1.000000e-24 kJ |
| 5 zJ | 5.000000e-24 kJ |
| 10 zJ | 1.000000e-23 kJ |
| 20 zJ | 2.000000e-23 kJ |
| 50 zJ | 5.000000e-23 kJ |
| 100 zJ | 1.000000e-22 kJ |
| 500 zJ | 5.000000e-22 kJ |
| 1000 zJ | 1.000000e-21 kJ |
Related conversions
Reserved between the cards and the FAQ so the page stays balanced.
How the formula works
Both zeptojoule and kilojoule measure the same physical quantity, so converting between them is a single multiplication. Multiply a value in zeptojoules by 1.000000000e-24 to get kilojoules. To reverse the conversion, multiply a kilojoule value by 1.000000000e+24 to get back to zeptojoules.
Frequently asked questions
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.
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 zeptojoules to kilojoules?
Multiply the zeptojoule value by 1.000000000e-24 to get the equivalent in kilojoules. For example, 5 zJ × 1.000000000e-24 = 5.000000e-24 kJ.
Is this conversion exact?
Yes. Both units are defined against the SI base unit for this dimension, so the factor 1.000000000e-24 is an exact, non-rounded value.
Can I convert kilojoules back to zeptojoules?
Yes. Divide the kilojoule value by 1.000000000e-24, or multiply it by 1.000000000e+24, to get zeptojoules.
Reserved between the FAQ and the article so the page stays balanced.
About converting zeptojoules to kilojoules
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. A kilojoule (kJ) equals 1,000 joules and is commonly used on nutrition labels outside the United States.
Use this calculator to move between zeptojoules 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.