Microjoule is 0.000001 joule units.
Microjoules to Millijoules Converter — uJ to mJ
Convert Microjoule (uJ) to Millijoule (mJ) using the exact conversion factor (1 microjoule = 0.001 millijoule). See the formula, worked examples, and conversion table.
Microjoules to Millijoules converter
Converter
Energy Converter
Convert joules, calories, kilowatt-hours, BTU, electronvolts, therms, and mechanical work units.
Context values
Some unit families need one extra value for a physically accurate result.
Millijoule is 0.001 joule units.
Result = input x 1e-6 / 0.001.
Energy uses the joule as the base unit.
Reserved above the conversion cards and below the converter.
About Converting Microjoules to Millijoules
Microjoule and Millijoule both measure energy, and the conversion is especially useful for comparing nutrition labels (kilocalories) against scientific energy figures (joules). Specifically: Microjoule is 0.000001 joule units, and millijoule is 0.001 joule units.
Formula
millijoules = microjoules × 0.001
This factor comes from each unit's defined relationship to the category's base unit: 1 microjoule equals 0.000001 base units, and 1 millijoule equals 0.001 base units, so dividing one by the other gives the direct microjoule-to-millijoule factor of 0.001.
Simple example
1 uJ × 0.001 = 0.001 mJ
1 microjoule = 0.001 millijoules.
Real-world example
100 uJ × 0.001 = 0.1 mJ
100 microjoules = 0.1 millijoules.
Conversion table
| Microjoule (uJ) | Millijoule (mJ) |
|---|---|
| 1 uJ | 0.001 mJ |
| 10 uJ | 0.01 mJ |
| 100 uJ | 0.1 mJ |
| 500 uJ | 0.5 mJ |
| 1,000 uJ | 1 mJ |
| 2,000 uJ | 2 mJ |
Reverse conversion: Millijoule to Microjoule
0.001 mJ × 1000 = 1 uJ
0.001 millijoules = 1 microjoule.
microjoules = millijoules × 1000
For a page dedicated to this direction, see Millijoule to Microjoule.
Understanding the Microjoule (uJ)
Microjoule is 0.000001 joule units.
Understanding the Millijoule (mJ)
Millijoule is 0.001 joule units.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many millijoules are in 1 microjoule?
1 microjoule equals 0.001 millijoules, using the exact defined conversion factor rather than an estimate.
How do I convert microjoule to millijoule?
Multiply the microjoule value by 0.001. The converter above does this instantly to whatever precision you set.
How do I convert millijoule back to microjoule?
Use the reverse factor: 1 millijoule equals 1,000 microjoules. You can also use the swap control in the converter above to flip the direction instantly.
What is a microjoule?
Microjoule (uJ) is a unit of energy.
What is a millijoule?
Millijoule (mJ) is a unit of energy.
Is the microjoule to millijoule conversion exact?
Yes. Both microjoule and millijoule are defined by fixed standards rather than physical artifacts, so the factor of 0.001 used above is exact to as many digits as you choose to display.