The joule (J) is the SI derived unit of energy, equal to the work done when a force of one newton acts over one meter.
Joules to Millijoules
Convert Joule (J) to Millijoule (mJ) instantly with an exact formula, conversion table, and FAQ.
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Convert joules (J) to millijoules (mJ) instantly with formula, conversion table, and FAQ.
Context values
Some unit families need one extra value for a physically accurate result.
A millijoule (mJ) is a metric-prefixed unit of energy equal to 10-3 joules, a fraction of a single joule, using the SI milli prefix.
mJ = J × 1000
Results update instantly for Joules to Millijoules conversions.
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Formula
mJ = J × 1000
J = mJ × 0.001
Conversion table
| 1 J | 1000 mJ |
| 5 J | 5000 mJ |
| 10 J | 10000 mJ |
| 20 J | 20000 mJ |
| 50 J | 50000 mJ |
| 100 J | 100000 mJ |
| 500 J | 500000 mJ |
| 1000 J | 1.000000e+06 mJ |
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How the formula works
Both joule and millijoule measure the same physical quantity, so converting between them is a single multiplication. Multiply a value in joules by 1000 to get millijoules. To reverse the conversion, multiply a millijoule value by 0.001 to get back to joules.
Frequently asked questions
What is Joule (J)?
The joule (J) is the SI derived unit of energy, equal to the work done when a force of one newton acts over one meter.
What is Millijoule (mJ)?
A millijoule (mJ) is a metric-prefixed unit of energy equal to 10-3 joules, a fraction of a single joule, using the SI milli prefix.
How do I convert joules to millijoules?
Multiply the joule value by 1000 to get the equivalent in millijoules. For example, 5 J × 1000 = 5000 mJ.
Is this conversion exact?
Yes. Both units are defined against the SI base unit for this dimension, so the factor 1000 is an exact, non-rounded value.
Can I convert millijoules back to joules?
Yes. Divide the millijoule value by 1000, or multiply it by 0.001, to get joules.
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About converting joules to millijoules
The joule (J) is the SI derived unit of energy, equal to the work done when a force of one newton acts over one meter. A millijoule (mJ) is a metric-prefixed unit of energy equal to 10-3 joules, a fraction of a single joule, using the SI milli prefix.
Use this calculator to move between joules and millijoules accurately for homework, engineering, billing, or everyday energy calculations. The Universal Converter uses exact unit factors, so results stay consistent across the site.