A gigajoule (GJ) is a metric-prefixed unit of energy equal to 109 joules, using the SI giga prefix.
Gigajoules to Megajoules
Convert Gigajoule (GJ) to Megajoule (MJ) instantly with an exact formula, conversion table, and FAQ.
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Convert gigajoules (GJ) to megajoules (MJ) instantly with formula, conversion table, and FAQ.
Context values
Some unit families need one extra value for a physically accurate result.
A megajoule (MJ) is a metric-prefixed unit of energy equal to 106 joules, using the SI mega prefix.
MJ = GJ × 1000
Results update instantly for Gigajoules to Megajoules conversions.
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Formula
MJ = GJ × 1000
GJ = MJ × 0.001
Conversion table
| 1 GJ | 1000 MJ |
| 5 GJ | 5000 MJ |
| 10 GJ | 10000 MJ |
| 20 GJ | 20000 MJ |
| 50 GJ | 50000 MJ |
| 100 GJ | 100000 MJ |
| 500 GJ | 500000 MJ |
| 1000 GJ | 1.000000e+06 MJ |
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How the formula works
Both gigajoule and megajoule measure the same physical quantity, so converting between them is a single multiplication. Multiply a value in gigajoules by 1000 to get megajoules. To reverse the conversion, multiply a megajoule value by 0.001 to get back to gigajoules.
Frequently asked questions
What is Gigajoule (GJ)?
A gigajoule (GJ) is a metric-prefixed unit of energy equal to 109 joules, using the SI giga prefix.
What is Megajoule (MJ)?
A megajoule (MJ) is a metric-prefixed unit of energy equal to 106 joules, using the SI mega prefix.
How do I convert gigajoules to megajoules?
Multiply the gigajoule value by 1000 to get the equivalent in megajoules. For example, 5 GJ × 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 megajoules back to gigajoules?
Yes. Divide the megajoule value by 1000, or multiply it by 0.001, to get gigajoules.
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About converting gigajoules to megajoules
A gigajoule (GJ) is a metric-prefixed unit of energy equal to 109 joules, using the SI giga prefix. A megajoule (MJ) is a metric-prefixed unit of energy equal to 106 joules, using the SI mega prefix.
Use this calculator to move between gigajoules and megajoules accurately for homework, engineering, billing, or everyday energy calculations. The Universal Converter uses exact unit factors, so results stay consistent across the site.