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 Gigajoules
Convert Millijoule (mJ) to Gigajoule (GJ) instantly with an exact formula, conversion table, and FAQ.
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Convert millijoules (mJ) to gigajoules (GJ) instantly with formula, conversion table, and FAQ.
Context values
Some unit families need one extra value for a physically accurate result.
A gigajoule (GJ) is a metric-prefixed unit of energy equal to 109 joules, using the SI giga prefix.
GJ = mJ × 1.000000000e-12
Results update instantly for Millijoules to Gigajoules conversions.
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Formula
GJ = mJ × 1.000000000e-12
mJ = GJ × 1000000000000
Conversion table
| 1 mJ | 1.000000e-12 GJ |
| 5 mJ | 5.000000e-12 GJ |
| 10 mJ | 1.000000e-11 GJ |
| 20 mJ | 2.000000e-11 GJ |
| 50 mJ | 5.000000e-11 GJ |
| 100 mJ | 1.000000e-10 GJ |
| 500 mJ | 5.000000e-10 GJ |
| 1000 mJ | 1.000000e-09 GJ |
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How the formula works
Both millijoule and gigajoule measure the same physical quantity, so converting between them is a single multiplication. Multiply a value in millijoules by 1.000000000e-12 to get gigajoules. To reverse the conversion, multiply a gigajoule value by 1000000000000 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 Gigajoule (GJ)?
A gigajoule (GJ) is a metric-prefixed unit of energy equal to 109 joules, using the SI giga prefix.
How do I convert millijoules to gigajoules?
Multiply the millijoule value by 1.000000000e-12 to get the equivalent in gigajoules. For example, 5 mJ × 1.000000000e-12 = 5.000000e-12 GJ.
Is this conversion exact?
Yes. Both units are defined against the SI base unit for this dimension, so the factor 1.000000000e-12 is an exact, non-rounded value.
Can I convert gigajoules back to millijoules?
Yes. Divide the gigajoule value by 1.000000000e-12, or multiply it by 1000000000000, to get millijoules.
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About converting millijoules to gigajoules
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. A gigajoule (GJ) is a metric-prefixed unit of energy equal to 109 joules, using the SI giga prefix.
Use this calculator to move between millijoules and gigajoules accurately for homework, engineering, billing, or everyday energy calculations. The Universal Converter uses exact unit factors, so results stay consistent across the site.