Millijoule is 0.001 joule units.
Millijoules to Attojoules Converter — mJ to aJ
Convert Millijoule (mJ) to Attojoule (aJ) using the exact conversion factor (1 millijoule = 1e+15 attojoule). See the formula, worked examples, and conversion table.
Millijoules to Attojoules 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.
Attojoule is 1e-18 joule units.
Result = input x 0.001 / 1e-18.
Energy uses the joule as the base unit.
Reserved above the conversion cards and below the converter.
About Converting Millijoules to Attojoules
Millijoule and Attojoule both measure energy, and the conversion is especially useful for comparing nutrition labels (kilocalories) against scientific energy figures (joules). Specifically: Millijoule is 0.001 joule units, and attojoule is 1e-18 joule units.
Formula
attojoules = millijoules × 1e+15
This factor comes from each unit's defined relationship to the category's base unit: 1 millijoule equals 0.001 base units, and 1 attojoule equals 1e-18 base units, so dividing one by the other gives the direct millijoule-to-attojoule factor of 1e+15.
Simple example
1 mJ × 1e+15 = 1e+15 aJ
1 millijoule = 1e+15 attojoules.
Real-world example
100 mJ × 1e+15 = 1e+17 aJ
100 millijoules = 1e+17 attojoules.
Conversion table
| Millijoule (mJ) | Attojoule (aJ) |
|---|---|
| 1 mJ | 1e+15 aJ |
| 10 mJ | 1e+16 aJ |
| 100 mJ | 1e+17 aJ |
| 500 mJ | 5e+17 aJ |
| 1,000 mJ | 1e+18 aJ |
| 2,000 mJ | 2e+18 aJ |
Reverse conversion: Attojoule to Millijoule
1e+15 aJ × 1e-15 = 1 mJ
1e+15 attojoules = 1 millijoule.
millijoules = attojoules × 1e-15
For a page dedicated to this direction, see Attojoule to Millijoule.
Understanding the Millijoule (mJ)
Millijoule is 0.001 joule units.
Understanding the Attojoule (aJ)
Attojoule is 1e-18 joule units.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many attojoules are in 1 millijoule?
1 millijoule equals 1e+15 attojoules, using the exact defined conversion factor rather than an estimate.
How do I convert millijoule to attojoule?
Multiply the millijoule value by 1e+15. The converter above does this instantly to whatever precision you set.
How do I convert attojoule back to millijoule?
Use the reverse factor: 1 attojoule equals 1e-15 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 energy.
What is a attojoule?
Attojoule (aJ) is a unit of energy.
Is the millijoule to attojoule conversion exact?
Yes. Both millijoule and attojoule are defined by fixed standards rather than physical artifacts, so the factor of 1e+15 used above is exact to as many digits as you choose to display.