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 Kilocalories
Convert Femtojoule (fJ) to Kilocalorie (kcal) instantly with an exact formula, conversion table, and FAQ.
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Convert femtojoules (fJ) to kilocalories (kcal) instantly with formula, conversion table, and FAQ.
Context values
Some unit families need one extra value for a physically accurate result.
A kilocalorie (kcal) equals 1,000 small calories and is the unit behind the food "Calorie" shown on nutrition labels.
kcal = fJ × 2.390057361e-19
Results update instantly for Femtojoules to Kilocalories conversions.
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Formula
kcal = fJ × 2.390057361e-19
fJ = kcal × 4.184000000e+18
Conversion table
| 1 fJ | 2.390057e-19 kcal |
| 5 fJ | 1.195029e-18 kcal |
| 10 fJ | 2.390057e-18 kcal |
| 20 fJ | 4.780115e-18 kcal |
| 50 fJ | 1.195029e-17 kcal |
| 100 fJ | 2.390057e-17 kcal |
| 500 fJ | 1.195029e-16 kcal |
| 1000 fJ | 2.390057e-16 kcal |
Related conversions
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How the formula works
Both femtojoule and kilocalorie measure the same physical quantity, so converting between them is a single multiplication. Multiply a value in femtojoules by 2.390057361e-19 to get kilocalories. To reverse the conversion, multiply a kilocalorie value by 4.184000000e+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 Kilocalorie (kcal)?
A kilocalorie (kcal) equals 1,000 small calories and is the unit behind the food "Calorie" shown on nutrition labels.
How do I convert femtojoules to kilocalories?
Multiply the femtojoule value by 2.390057361e-19 to get the equivalent in kilocalories. For example, 5 fJ × 2.390057361e-19 = 1.195029e-18 kcal.
Is this conversion exact?
Yes. Both units are defined against the SI base unit for this dimension, so the factor 2.390057361e-19 is an exact, non-rounded value.
Can I convert kilocalories back to femtojoules?
Yes. Divide the kilocalorie value by 2.390057361e-19, or multiply it by 4.184000000e+18, to get femtojoules.
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About converting femtojoules to kilocalories
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 kilocalorie (kcal) equals 1,000 small calories and is the unit behind the food "Calorie" shown on nutrition labels.
Use this calculator to move between femtojoules and kilocalories accurately for homework, engineering, billing, or everyday energy calculations. The Universal Converter uses exact unit factors, so results stay consistent across the site.