The watt is one joule per second.
Watts to Zeptowatts Converter — W to zW
Convert Watt (W) to Zeptowatt (zW) using the exact conversion factor (1 watt = 1e+21 zeptowatt). See the formula, worked examples, conversion table, history, and common uses.
Watts to Zeptowatts 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.
Zeptowatt is 1e-21 watt units.
Result = input x 1 / 1e-21.
Power units are compatible.
Reserved above the conversion cards and below the converter.
About Converting Watts to Zeptowatts
Watt and Zeptowatt 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. Watt is most often used for electrical appliance power ratings worldwide.
Formula
zeptowatts = watts × 1e+21
This factor comes from each unit's defined relationship to the category's base unit: 1 watt equals 1 base unit, and 1 zeptowatt equals 1e-21 base units, so dividing one by the other gives the direct watt-to-zeptowatt factor of 1e+21.
Simple example
1 W × 1e+21 = 1e+21 zW
1 watt = 1e+21 zeptowatts.
Real-world example
100 W × 1e+21 = 1e+23 zW
100 watts = 1e+23 zeptowatts.
Conversion table
| Watt (W) | Zeptowatt (zW) |
|---|---|
| 1 W | 1e+21 zW |
| 10 W | 1e+22 zW |
| 50 W | 5e+22 zW |
| 100 W | 1e+23 zW |
| 500 W | 5e+23 zW |
| 1,000 W | 1e+24 zW |
Reverse conversion: Zeptowatt to Watt
1e+21 zW × 1e-21 = 1 W
1e+21 zeptowatts = 1 watts.
watts = zeptowatts × 1e-21
For a page dedicated to this direction, see Zeptowatt to Watt.
Understanding the Watt
Watt (W) measures power. The watt is the SI derived unit of power: one joule of energy per second. It is classified as a SI derived unit.
Where it's used: Standard scientific and everyday power unit worldwide
Uses of the Watt today
- Electrical appliance power ratings worldwide
- Light bulb brightness-equivalent labeling
- Engine and motor power specifications (alongside horsepower)
History of the Watt
The watt is named after James Watt, whose improvements to the steam engine in the late 18th century were commercially pivotal; ironically, Watt himself used horsepower (a unit he helped popularize) to market his engines. The watt was formally adopted as a unit at the 1889 General Conference on Weights and Measures and became the SI derived unit of power in the 20th century.
Historical origin. Watt was not the invention of a single named person; it developed through the process described above.
Understanding the Zeptowatt (zW)
Zeptowatt is 1e-21 watt units.
Watt — sources
- BIPM SI Brochure — Coherent derived units — Defines the watt as the SI unit of power.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many zeptowatts are in 1 watt?
1 watt equals 1e+21 zeptowatts, using the exact defined conversion factor rather than an estimate.
How do I convert watt to zeptowatt?
Multiply the watt value by 1e+21. The converter above does this instantly to whatever precision you set.
How do I convert zeptowatt back to watt?
Use the reverse factor: 1 zeptowatt equals 1e-21 watts. You can also use the swap control in the converter above to flip the direction instantly.
What is a watt?
Watt (W) measures power. The watt is the SI derived unit of power: one joule of energy per second. It is classified as a SI derived unit.
What is a zeptowatt?
Zeptowatt (zW) is a unit of engineering.
Is the watt to zeptowatt conversion exact?
Yes. Both watt and zeptowatt are defined by fixed standards rather than physical artifacts, so the factor of 1e+21 used above is exact to as many digits as you choose to display.
Where is the watt still used today?
Standard scientific and everyday power unit worldwide
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.