A femtojoule (fJ) is a metric-prefixed unit of energy equal to 10-15 joules, a fraction of a single joule, using the SI femto prefix.
Femtojoules to Kilojoules
Convert Femtojoule (fJ) to Kilojoule (kJ) instantly with an exact formula, conversion table, and FAQ.
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Convert femtojoules (fJ) 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 = fJ × 1.000000000e-18
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Formula
kJ = fJ × 1.000000000e-18
fJ = kJ × 1.000000000e+18
Conversion table
| 1 fJ | 1.000000e-18 kJ |
| 5 fJ | 5.000000e-18 kJ |
| 10 fJ | 1.000000e-17 kJ |
| 20 fJ | 2.000000e-17 kJ |
| 50 fJ | 5.000000e-17 kJ |
| 100 fJ | 1.000000e-16 kJ |
| 500 fJ | 5.000000e-16 kJ |
| 1000 fJ | 1.000000e-15 kJ |
Related conversions
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How the formula works
Both femtojoule and kilojoule measure the same physical quantity, so converting between them is a single multiplication. Multiply a value in femtojoules by 1.000000000e-18 to get kilojoules. To reverse the conversion, multiply a kilojoule value by 1.000000000e+18 to get back to femtojoules.
Frequently asked questions
What is Femtojoule (fJ)?
A femtojoule (fJ) is a metric-prefixed unit of energy equal to 10-15 joules, a fraction of a single joule, using the SI femto 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 femtojoules to kilojoules?
Multiply the femtojoule value by 1.000000000e-18 to get the equivalent in kilojoules. For example, 5 fJ × 1.000000000e-18 = 5.000000e-18 kJ.
Is this conversion exact?
Yes. Both units are defined against the SI base unit for this dimension, so the factor 1.000000000e-18 is an exact, non-rounded value.
Can I convert kilojoules back to femtojoules?
Yes. Divide the kilojoule value by 1.000000000e-18, or multiply it by 1.000000000e+18, to get femtojoules.
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About converting femtojoules to kilojoules
A femtojoule (fJ) is a metric-prefixed unit of energy equal to 10-15 joules, a fraction of a single joule, using the SI femto 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 femtojoules 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.