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 Femtojoules
Convert Calorie (cal) to Femtojoule (fJ) instantly with an exact formula, conversion table, and FAQ.
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Convert calories (cal) to femtojoules (fJ) instantly with formula, conversion table, and FAQ.
Context values
Some unit families need one extra value for a physically accurate result.
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.
fJ = cal × 4.184000000e+15
Results update instantly for Calories to Femtojoules conversions.
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Formula
fJ = cal × 4.184000000e+15
cal = fJ × 2.390057361e-16
Conversion table
| 1 cal | 4.184000e+15 fJ |
| 5 cal | 2.092000e+16 fJ |
| 10 cal | 4.184000e+16 fJ |
| 20 cal | 8.368000e+16 fJ |
| 50 cal | 2.092000e+17 fJ |
| 100 cal | 4.184000e+17 fJ |
| 500 cal | 2.092000e+18 fJ |
| 1000 cal | 4.184000e+18 fJ |
Related conversions
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How the formula works
Both calorie and femtojoule measure the same physical quantity, so converting between them is a single multiplication. Multiply a value in calories by 4.184000000e+15 to get femtojoules. To reverse the conversion, multiply a femtojoule value by 2.390057361e-16 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 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.
How do I convert calories to femtojoules?
Multiply the calorie value by 4.184000000e+15 to get the equivalent in femtojoules. For example, 5 cal × 4.184000000e+15 = 2.092000e+16 fJ.
Is this conversion exact?
Yes. Both units are defined against the SI base unit for this dimension, so the factor 4.184000000e+15 is an exact, non-rounded value.
Can I convert femtojoules back to calories?
Yes. Divide the femtojoule value by 4.184000000e+15, or multiply it by 2.390057361e-16, to get calories.
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About converting calories to femtojoules
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 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.
Use this calculator to move between calories and femtojoules accurately for homework, engineering, billing, or everyday energy calculations. The Universal Converter uses exact unit factors, so results stay consistent across the site.