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 Watt hours
Convert Millijoule (mJ) to Watt-hour (Wh) instantly with an exact formula, conversion table, and FAQ.
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Convert millijoules (mJ) to watt hours (Wh) instantly with formula, conversion table, and FAQ.
Context values
Some unit families need one extra value for a physically accurate result.
A watt-hour (Wh) is the energy delivered by one watt of power sustained for one hour, equal to 3,600 joules.
Wh = mJ × 2.777777778e-07
Results update instantly for Millijoules to Watt hours conversions.
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Formula
Wh = mJ × 2.777777778e-07
mJ = Wh × 3600000
Conversion table
| 1 mJ | 2.777778e-07 Wh |
| 5 mJ | 0.000001 Wh |
| 10 mJ | 0.000003 Wh |
| 20 mJ | 0.000006 Wh |
| 50 mJ | 0.000014 Wh |
| 100 mJ | 0.000028 Wh |
| 500 mJ | 0.000139 Wh |
| 1000 mJ | 0.000278 Wh |
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How the formula works
Both millijoule and watt-hour measure the same physical quantity, so converting between them is a single multiplication. Multiply a value in millijoules by 2.777777778e-07 to get watt hours. To reverse the conversion, multiply a watt-hour value by 3600000 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 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.
How do I convert millijoules to watt hours?
Multiply the millijoule value by 2.777777778e-07 to get the equivalent in watt hours. For example, 5 mJ × 2.777777778e-07 = 0.000001 Wh.
Is this conversion exact?
Yes. Both units are defined against the SI base unit for this dimension, so the factor 2.777777778e-07 is an exact, non-rounded value.
Can I convert watt hours back to millijoules?
Yes. Divide the watt-hour value by 2.777777778e-07, or multiply it by 3600000, to get millijoules.
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About converting millijoules to watt hours
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 watt-hour (Wh) is the energy delivered by one watt of power sustained for one hour, equal to 3,600 joules.
Use this calculator to move between millijoules and watt hours accurately for homework, engineering, billing, or everyday energy calculations. The Universal Converter uses exact unit factors, so results stay consistent across the site.