Zeptowatt is 1e-21 watt units.
Zeptowatts to Milliwatts Converter — zW to mW
Convert Zeptowatt (zW) to Milliwatt (mW) using the exact conversion factor (1 zeptowatt = 1e-18 milliwatt). See the formula, worked examples, and conversion table.
Zeptowatts to Milliwatts 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.
Milliwatt is 0.001 watt units.
Result = input x 1e-21 / 0.001.
Power units are compatible.
Reserved above the conversion cards and below the converter.
About Converting Zeptowatts to Milliwatts
Zeptowatt and Milliwatt 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: Zeptowatt is 1e-21 watt units, and milliwatt is 0.001 watt units.
Formula
milliwatts = zeptowatts × 1e-18
This factor comes from each unit's defined relationship to the category's base unit: 1 zeptowatt equals 1e-21 base units, and 1 milliwatt equals 0.001 base units, so dividing one by the other gives the direct zeptowatt-to-milliwatt factor of 1e-18.
Simple example
1 zW × 1e-18 = 1e-18 mW
1 zeptowatt = 1e-18 milliwatts.
Real-world example
100 zW × 1e-18 = 1e-16 mW
100 zeptowatts = 1e-16 milliwatts.
Conversion table
| Zeptowatt (zW) | Milliwatt (mW) |
|---|---|
| 1 zW | 1e-18 mW |
| 10 zW | 1e-17 mW |
| 50 zW | 5e-17 mW |
| 100 zW | 1e-16 mW |
| 500 zW | 5e-16 mW |
| 1,000 zW | 1e-15 mW |
Reverse conversion: Milliwatt to Zeptowatt
1e-18 mW × 1e+18 = 1 zW
1e-18 milliwatts = 1 zeptowatts.
zeptowatts = milliwatts × 1e+18
For a page dedicated to this direction, see Milliwatt to Zeptowatt.
Understanding the Zeptowatt (zW)
Zeptowatt is 1e-21 watt units.
Understanding the Milliwatt (mW)
Milliwatt is 0.001 watt units.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many milliwatts are in 1 zeptowatt?
1 zeptowatt equals 1e-18 milliwatts, using the exact defined conversion factor rather than an estimate.
How do I convert zeptowatt to milliwatt?
Multiply the zeptowatt value by 1e-18. The converter above does this instantly to whatever precision you set.
How do I convert milliwatt back to zeptowatt?
Use the reverse factor: 1 milliwatt equals 1e+18 zeptowatts. You can also use the swap control in the converter above to flip the direction instantly.
What is a zeptowatt?
Zeptowatt (zW) is a unit of engineering.
What is a milliwatt?
Milliwatt (mW) is a unit of engineering.
Is the zeptowatt to milliwatt conversion exact?
Yes. Both zeptowatt and milliwatt are defined by fixed standards rather than physical artifacts, so the factor of 1e-18 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.