An erg is a CGS energy unit.
Ergs to Millijoules Converter — erg to mJ
Convert Erg (erg) to Millijoule (mJ) using the exact conversion factor (1 erg = 0.0001 millijoule). See the formula, worked examples, and conversion table.
Ergs 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-7 / 0.001.
Energy units are compatible.
Reserved above the conversion cards and below the converter.
About Converting Ergs to Millijoules
Erg 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: An erg is a CGS energy unit, and millijoule is 0.001 joule units.
Formula
millijoules = ergs × 0.0001
This factor comes from each unit's defined relationship to the category's base unit: 1 erg equals 1e-7 base units, and 1 millijoule equals 0.001 base units, so dividing one by the other gives the direct erg-to-millijoule factor of 0.0001.
Simple example
1 erg × 0.0001 = 0.0001 mJ
1 erg = 0.0001 millijoules.
Real-world example
100 erg × 0.0001 = 0.01 mJ
100 ergs = 0.01 millijoules.
Conversion table
| Erg (erg) | Millijoule (mJ) |
|---|---|
| 1 erg | 0.0001 mJ |
| 10 erg | 0.001 mJ |
| 50 erg | 0.005 mJ |
| 100 erg | 0.01 mJ |
| 500 erg | 0.05 mJ |
| 1,000 erg | 0.1 mJ |
Reverse conversion: Millijoule to Erg
0.0001 mJ × 10000 = 1 erg
0.0001 millijoules = 1 ergs.
ergs = millijoules × 10000
For a page dedicated to this direction, see Millijoule to Erg.
Understanding the Erg (erg)
An erg is a CGS energy unit.
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 erg?
1 erg equals 0.0001 millijoules, using the exact defined conversion factor rather than an estimate.
How do I convert erg to millijoule?
Multiply the erg value by 0.0001. The converter above does this instantly to whatever precision you set.
How do I convert millijoule back to erg?
Use the reverse factor: 1 millijoule equals 10,000 ergs. You can also use the swap control in the converter above to flip the direction instantly.
What is a erg?
Erg (erg) is a unit of engineering.
What is a millijoule?
Millijoule (mJ) is a unit of engineering.
Is the erg to millijoule conversion exact?
Yes. Both erg and millijoule are defined by fixed standards rather than physical artifacts, so the factor of 0.0001 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.