A megajoule (MJ) is a metric-prefixed unit of energy equal to 106 joules, using the SI mega prefix.
Megajoules to Gigajoules
Convert Megajoule (MJ) to Gigajoule (GJ) instantly with an exact formula, conversion table, and FAQ.
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Convert megajoules (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 × 0.001
Results update instantly for Megajoules to Gigajoules conversions.
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Formula
GJ = MJ × 0.001
MJ = GJ × 1000
Conversion table
| 1 MJ | 0.001000 GJ |
| 5 MJ | 0.005000 GJ |
| 10 MJ | 0.010000 GJ |
| 20 MJ | 0.020000 GJ |
| 50 MJ | 0.050000 GJ |
| 100 MJ | 0.100000 GJ |
| 500 MJ | 0.500000 GJ |
| 1000 MJ | 1 GJ |
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How the formula works
Both megajoule and gigajoule measure the same physical quantity, so converting between them is a single multiplication. Multiply a value in megajoules by 0.001 to get gigajoules. To reverse the conversion, multiply a gigajoule value by 1000 to get back to megajoules.
Frequently asked questions
What is Megajoule (MJ)?
A megajoule (MJ) is a metric-prefixed unit of energy equal to 106 joules, using the SI mega 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 megajoules to gigajoules?
Multiply the megajoule value by 0.001 to get the equivalent in gigajoules. For example, 5 MJ × 0.001 = 0.005000 GJ.
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 gigajoules back to megajoules?
Yes. Divide the gigajoule value by 0.001, or multiply it by 1000, to get megajoules.
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About converting megajoules to gigajoules
A megajoule (MJ) is a metric-prefixed unit of energy equal to 106 joules, using the SI mega 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 megajoules 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.