Millijoule is 0.001 joule units.
Millijoules to Kilojoules Converter — mJ to kJ
Convert Millijoule (mJ) to Kilojoule (kJ) using the exact conversion factor (1 millijoule = 0.000001 kilojoule). See the formula, worked examples, and conversion table.
Millijoules to Kilojoules 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.
Kilojoule is 1000 joule units.
Result = input x 0.001 / 1000.
Energy units are compatible.
Reserved above the conversion cards and below the converter.
About Converting Millijoules to Kilojoules
Millijoule and Kilojoule 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 kilojoule is 1000 joule units.
Formula
kilojoules = millijoules × 0.000001
This factor comes from each unit's defined relationship to the category's base unit: 1 millijoule equals 0.001 base units, and 1 kilojoule equals 1000 base units, so dividing one by the other gives the direct millijoule-to-kilojoule factor of 0.000001.
Simple example
1 mJ × 0.000001 = 0.000001 kJ
1 millijoule = 0.000001 kilojoules.
Real-world example
100 mJ × 0.000001 = 0.0001 kJ
100 millijoules = 0.0001 kilojoules.
Conversion table
| Millijoule (mJ) | Kilojoule (kJ) |
|---|---|
| 1 mJ | 0.000001 kJ |
| 10 mJ | 0.00001 kJ |
| 50 mJ | 0.00005 kJ |
| 100 mJ | 0.0001 kJ |
| 500 mJ | 0.0005 kJ |
| 1,000 mJ | 0.001 kJ |
Reverse conversion: Kilojoule to Millijoule
0.000001 kJ × 1000000 = 1 mJ
0.000001 kilojoules = 1 millijoule.
millijoules = kilojoules × 1000000
For a page dedicated to this direction, see Kilojoule to Millijoule.
Understanding the Millijoule (mJ)
Millijoule is 0.001 joule units.
Understanding the Kilojoule (kJ)
Kilojoule is 1000 joule units.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many kilojoules are in 1 millijoule?
1 millijoule equals 0.000001 kilojoules, using the exact defined conversion factor rather than an estimate.
How do I convert millijoule to kilojoule?
Multiply the millijoule value by 0.000001. The converter above does this instantly to whatever precision you set.
How do I convert kilojoule back to millijoule?
Use the reverse factor: 1 kilojoule equals 1,000,000 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 kilojoule?
Kilojoule (kJ) is a unit of engineering.
Is the millijoule to kilojoule conversion exact?
Yes. Both millijoule and kilojoule are defined by fixed standards rather than physical artifacts, so the factor of 0.000001 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.