A watt-hour (Wh) is the energy delivered by one watt of power sustained for one hour, equal to 3,600 joules.
Watt hours to Millijoules
Convert Watt-hour (Wh) to Millijoule (mJ) instantly with an exact formula, conversion table, and FAQ.
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Convert watt hours (Wh) 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 = Wh × 3600000
Results update instantly for Watt hours to Millijoules conversions.
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Formula
mJ = Wh × 3600000
Wh = mJ × 2.777777778e-07
Conversion table
| 1 Wh | 3.600000e+06 mJ |
| 5 Wh | 1.800000e+07 mJ |
| 10 Wh | 3.600000e+07 mJ |
| 20 Wh | 7.200000e+07 mJ |
| 50 Wh | 1.800000e+08 mJ |
| 100 Wh | 3.600000e+08 mJ |
| 500 Wh | 1.800000e+09 mJ |
| 1000 Wh | 3.600000e+09 mJ |
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How the formula works
Both watt-hour and millijoule measure the same physical quantity, so converting between them is a single multiplication. Multiply a value in watt hours by 3600000 to get millijoules. To reverse the conversion, multiply a millijoule value by 2.777777778e-07 to get back to watt hours.
Frequently asked questions
What is Watt-hour (Wh)?
A watt-hour (Wh) is the energy delivered by one watt of power sustained for one hour, equal to 3,600 joules.
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 watt hours to millijoules?
Multiply the watt-hour value by 3600000 to get the equivalent in millijoules. For example, 5 Wh × 3600000 = 1.800000e+07 mJ.
Is this conversion exact?
Yes. Both units are defined against the SI base unit for this dimension, so the factor 3600000 is an exact, non-rounded value.
Can I convert millijoules back to watt hours?
Yes. Divide the millijoule value by 3600000, or multiply it by 2.777777778e-07, to get watt hours.
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About converting watt hours to millijoules
A watt-hour (Wh) is the energy delivered by one watt of power sustained for one hour, equal to 3,600 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.
Use this calculator to move between watt hours 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.