Millijoule is 0.001 joule units.
Millijoules to Decijoules Converter — mJ to dJ
Convert Millijoule (mJ) to Decijoule (dJ) using the exact conversion factor (1 millijoule = 0.01 decijoule). See the formula, worked examples, and conversion table.
Millijoules to Decijoules converter
Converter
Engineering Converter
Convert common stress, force, torque, power, and energy units used in engineering.
Context values
Some unit families need one extra value for a physically accurate result.
Decijoule is 0.1 joule units.
Result = input x 0.001 / 0.1.
Energy units are compatible.
Reserved above the conversion cards and below the converter.
About Converting Millijoules to Decijoules
Millijoule and Decijoule both measure a quantity used in structural or mechanical engineering — commonly stress, pressure, force, torque, power, or energy — where converting between the unit conventions used in different regions, industries, or equipment specifications is a routine part of design work. Specifically: Millijoule is 0.001 joule units, and decijoule is 0.1 joule units.
Formula
decijoules = millijoules × 0.01
This factor comes from each unit's defined relationship to the category's base unit: 1 millijoule equals 0.001 base units, and 1 decijoule equals 0.1 base units, so dividing one by the other gives the direct millijoule-to-decijoule factor of 0.01.
Simple example
1 mJ × 0.01 = 0.01 dJ
1 millijoule = 0.01 decijoules.
Real-world example
100 mJ × 0.01 = 1 dJ
100 millijoules = 1 decijoule.
Conversion table
| Millijoule (mJ) | Decijoule (dJ) |
|---|---|
| 1 mJ | 0.01 dJ |
| 10 mJ | 0.1 dJ |
| 50 mJ | 0.5 dJ |
| 100 mJ | 1 dJ |
| 500 mJ | 5 dJ |
| 1,000 mJ | 10 dJ |
Reverse conversion: Decijoule to Millijoule
0.01 dJ × 100 = 1 mJ
0.01 decijoules = 1 millijoule.
millijoules = decijoules × 100
For a page dedicated to this direction, see Decijoule to Millijoule.
Understanding the Millijoule (mJ)
Millijoule is 0.001 joule units.
Understanding the Decijoule (dJ)
Decijoule is 0.1 joule units.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many decijoules are in 1 millijoule?
1 millijoule equals 0.01 decijoules, using the exact defined conversion factor rather than an estimate.
How do I convert millijoule to decijoule?
Multiply the millijoule value by 0.01. The converter above does this instantly to whatever precision you set.
How do I convert decijoule back to millijoule?
Use the reverse factor: 1 decijoule equals 100 millijoules. You can also use the swap control in the converter above to flip the direction instantly.
What is a millijoule?
Millijoule (mJ) is a unit of engineering.
What is a decijoule?
Decijoule (dJ) is a unit of engineering.
Is the millijoule to decijoule conversion exact?
Yes. Both millijoule and decijoule are defined by fixed standards rather than physical artifacts, so the factor of 0.01 used above is exact to as many digits as you choose to display.
Why do engineering unit conventions vary so much by region and industry?
Pressure, force, and stress can be expressed in metric (pascal, newton), US customary (psi, pound-force), or older and industry-specific units (atmosphere, torr, kip) depending on the country, industry, and even the equipment manufacturer, which is why engineers routinely need to convert between them when working across specs from different sources.