A attojoule (aJ) is a metric-prefixed unit of energy equal to 10-18 joules, a fraction of a single joule, using the SI atto prefix.
Attojoules to Calories
Convert Attojoule (aJ) to Calorie (cal) instantly with an exact formula, conversion table, and FAQ.
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Convert attojoules (aJ) to calories (cal) instantly with formula, conversion table, and FAQ.
Context values
Some unit families need one extra value for a physically accurate result.
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.
cal = aJ × 2.390057361e-19
Results update instantly for Attojoules to Calories conversions.
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Formula
cal = aJ × 2.390057361e-19
aJ = cal × 4.184000000e+18
Conversion table
| 1 aJ | 2.390057e-19 cal |
| 5 aJ | 1.195029e-18 cal |
| 10 aJ | 2.390057e-18 cal |
| 20 aJ | 4.780115e-18 cal |
| 50 aJ | 1.195029e-17 cal |
| 100 aJ | 2.390057e-17 cal |
| 500 aJ | 1.195029e-16 cal |
| 1000 aJ | 2.390057e-16 cal |
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How the formula works
Both attojoule and calorie measure the same physical quantity, so converting between them is a single multiplication. Multiply a value in attojoules by 2.390057361e-19 to get calories. To reverse the conversion, multiply a calorie value by 4.184000000e+18 to get back to attojoules.
Frequently asked questions
What is Attojoule (aJ)?
A attojoule (aJ) is a metric-prefixed unit of energy equal to 10-18 joules, a fraction of a single joule, using the SI atto prefix.
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.
How do I convert attojoules to calories?
Multiply the attojoule value by 2.390057361e-19 to get the equivalent in calories. For example, 5 aJ × 2.390057361e-19 = 1.195029e-18 cal.
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 calories back to attojoules?
Yes. Divide the calorie value by 2.390057361e-19, or multiply it by 4.184000000e+18, to get attojoules.
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About converting attojoules to calories
A attojoule (aJ) is a metric-prefixed unit of energy equal to 10-18 joules, a fraction of a single joule, using the SI atto prefix. 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.
Use this calculator to move between attojoules and calories accurately for homework, engineering, billing, or everyday energy calculations. The Universal Converter uses exact unit factors, so results stay consistent across the site.