Zeptojoule is 1e-21 joule units.
Zeptojoules to Attojoules Converter — zJ to aJ
Convert Zeptojoule (zJ) to Attojoule (aJ) using the exact conversion factor (1 zeptojoule = 0.001 attojoule). See the formula, worked examples, and conversion table.
Zeptojoules to Attojoules 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.
Attojoule is 1e-18 joule units.
Result = input x 1e-21 / 1e-18.
Energy units are compatible.
Reserved above the conversion cards and below the converter.
About Converting Zeptojoules to Attojoules
Zeptojoule and Attojoule 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: Zeptojoule is 1e-21 joule units, and attojoule is 1e-18 joule units.
Formula
attojoules = zeptojoules × 0.001
This factor comes from each unit's defined relationship to the category's base unit: 1 zeptojoule equals 1e-21 base units, and 1 attojoule equals 1e-18 base units, so dividing one by the other gives the direct zeptojoule-to-attojoule factor of 0.001.
Simple example
1 zJ × 0.001 = 0.001 aJ
1 zeptojoule = 0.001 attojoules.
Real-world example
100 zJ × 0.001 = 0.1 aJ
100 zeptojoules = 0.1 attojoules.
Conversion table
| Zeptojoule (zJ) | Attojoule (aJ) |
|---|---|
| 1 zJ | 0.001 aJ |
| 10 zJ | 0.01 aJ |
| 50 zJ | 0.05 aJ |
| 100 zJ | 0.1 aJ |
| 500 zJ | 0.5 aJ |
| 1,000 zJ | 1 aJ |
Reverse conversion: Attojoule to Zeptojoule
0.001 aJ × 1000 = 1 zJ
0.001 attojoules = 1 zeptojoules.
zeptojoules = attojoules × 1000
For a page dedicated to this direction, see Attojoule to Zeptojoule.
Understanding the Zeptojoule (zJ)
Zeptojoule is 1e-21 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 zeptojoule?
1 zeptojoule equals 0.001 attojoules, using the exact defined conversion factor rather than an estimate.
How do I convert zeptojoule to attojoule?
Multiply the zeptojoule value by 0.001. The converter above does this instantly to whatever precision you set.
How do I convert attojoule back to zeptojoule?
Use the reverse factor: 1 attojoule equals 1,000 zeptojoules. You can also use the swap control in the converter above to flip the direction instantly.
What is a zeptojoule?
Zeptojoule (zJ) is a unit of engineering.
What is a attojoule?
Attojoule (aJ) is a unit of engineering.
Is the zeptojoule to attojoule conversion exact?
Yes. Both zeptojoule and attojoule are defined by fixed standards rather than physical artifacts, so the factor of 0.001 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.