A megajoule (MJ) is a metric-prefixed unit of energy equal to 106 joules, using the SI mega prefix.
Megajoules to Millijoules
Convert Megajoule (MJ) to Millijoule (mJ) instantly with an exact formula, conversion table, and FAQ.
Reserved for a responsive leaderboard above the conversion details.
Professional calculator style
World-scale conversion engine
30+ categories
6,500+ units
Instant results
Offline ready
Energy calculator
Energy Converter
Convert megajoules (MJ) 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 = MJ × 1000000000
Results update instantly for Megajoules to Millijoules conversions.
Reserved above the conversion cards and below the converter.
Formula
mJ = MJ × 1000000000
MJ = mJ × 1.000000000e-09
Conversion table
| 1 MJ | 1.000000e+09 mJ |
| 5 MJ | 5.000000e+09 mJ |
| 10 MJ | 1.000000e+10 mJ |
| 20 MJ | 2.000000e+10 mJ |
| 50 MJ | 5.000000e+10 mJ |
| 100 MJ | 1.000000e+11 mJ |
| 500 MJ | 5.000000e+11 mJ |
| 1000 MJ | 1.000000e+12 mJ |
Related conversions
Reserved between the cards and the FAQ so the page stays balanced.
How the formula works
Both megajoule and millijoule measure the same physical quantity, so converting between them is a single multiplication. Multiply a value in megajoules by 1000000000 to get millijoules. To reverse the conversion, multiply a millijoule value by 1.000000000e-09 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 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 megajoules to millijoules?
Multiply the megajoule value by 1000000000 to get the equivalent in millijoules. For example, 5 MJ × 1000000000 = 5.000000e+09 mJ.
Is this conversion exact?
Yes. Both units are defined against the SI base unit for this dimension, so the factor 1000000000 is an exact, non-rounded value.
Can I convert millijoules back to megajoules?
Yes. Divide the millijoule value by 1000000000, or multiply it by 1.000000000e-09, to get megajoules.
Reserved between the FAQ and the article so the page stays balanced.
About converting megajoules to millijoules
A megajoule (MJ) is a metric-prefixed unit of energy equal to 106 joules, using the SI mega prefix. 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 megajoules 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.