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.
Millijoules to Joules
Convert Millijoule (mJ) to Joule (J) instantly with an exact formula, conversion table, and FAQ.
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Convert millijoules (mJ) to joules (J) instantly with formula, conversion table, and FAQ.
Context values
Some unit families need one extra value for a physically accurate result.
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.
J = mJ × 0.001
Results update instantly for Millijoules to Joules conversions.
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Formula
J = mJ × 0.001
mJ = J × 1000
Conversion table
| 1 mJ | 0.001000 J |
| 5 mJ | 0.005000 J |
| 10 mJ | 0.010000 J |
| 20 mJ | 0.020000 J |
| 50 mJ | 0.050000 J |
| 100 mJ | 0.100000 J |
| 500 mJ | 0.500000 J |
| 1000 mJ | 1 J |
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How the formula works
Both millijoule and joule measure the same physical quantity, so converting between them is a single multiplication. Multiply a value in millijoules by 0.001 to get joules. To reverse the conversion, multiply a joule value by 1000 to get back to millijoules.
Frequently asked questions
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.
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.
How do I convert millijoules to joules?
Multiply the millijoule value by 0.001 to get the equivalent in joules. For example, 5 mJ × 0.001 = 0.005000 J.
Is this conversion exact?
Yes. Both units are defined against the SI base unit for this dimension, so the factor 0.001 is an exact, non-rounded value.
Can I convert joules back to millijoules?
Yes. Divide the joule value by 0.001, or multiply it by 1000, to get millijoules.
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About converting millijoules to joules
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. 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.
Use this calculator to move between millijoules and joules accurately for homework, engineering, billing, or everyday energy calculations. The Universal Converter uses exact unit factors, so results stay consistent across the site.