Femtojoule is 1e-15 joule units.
Femtojoules to Millijoules Converter — fJ to mJ
Convert Femtojoule (fJ) to Millijoule (mJ) using the exact conversion factor (1 femtojoule = 1e-12 millijoule). See the formula, worked examples, and conversion table.
Femtojoules to Millijoules 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.
Millijoule is 0.001 joule units.
Result = input x 1e-15 / 0.001.
Energy units are compatible.
Reserved above the conversion cards and below the converter.
About Converting Femtojoules to Millijoules
Femtojoule and Millijoule 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: Femtojoule is 1e-15 joule units, and millijoule is 0.001 joule units.
Formula
millijoules = femtojoules × 1e-12
This factor comes from each unit's defined relationship to the category's base unit: 1 femtojoule equals 1e-15 base units, and 1 millijoule equals 0.001 base units, so dividing one by the other gives the direct femtojoule-to-millijoule factor of 1e-12.
Simple example
1 fJ × 1e-12 = 1e-12 mJ
1 femtojoule = 1e-12 millijoules.
Real-world example
100 fJ × 1e-12 = 1e-10 mJ
100 femtojoules = 1e-10 millijoules.
Conversion table
| Femtojoule (fJ) | Millijoule (mJ) |
|---|---|
| 1 fJ | 1e-12 mJ |
| 10 fJ | 1e-11 mJ |
| 50 fJ | 5e-11 mJ |
| 100 fJ | 1e-10 mJ |
| 500 fJ | 5e-10 mJ |
| 1,000 fJ | 1e-9 mJ |
Reverse conversion: Millijoule to Femtojoule
1e-12 mJ × 1e+12 = 1 fJ
1e-12 millijoules = 1 femtojoule.
femtojoules = millijoules × 1e+12
For a page dedicated to this direction, see Millijoule to Femtojoule.
Understanding the Femtojoule (fJ)
Femtojoule is 1e-15 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 femtojoule?
1 femtojoule equals 1e-12 millijoules, using the exact defined conversion factor rather than an estimate.
How do I convert femtojoule to millijoule?
Multiply the femtojoule value by 1e-12. The converter above does this instantly to whatever precision you set.
How do I convert millijoule back to femtojoule?
Use the reverse factor: 1 millijoule equals 1e+12 femtojoules. You can also use the swap control in the converter above to flip the direction instantly.
What is a femtojoule?
Femtojoule (fJ) is a unit of engineering.
What is a millijoule?
Millijoule (mJ) is a unit of engineering.
Is the femtojoule to millijoule conversion exact?
Yes. Both femtojoule and millijoule are defined by fixed standards rather than physical artifacts, so the factor of 1e-12 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.