Femtowatt is 1e-15 watt units.
Femtowatts to Watts Converter — fW to W
Convert Femtowatt (fW) to Watt (W) using the exact conversion factor (1 femtowatt = 1e-15 watt). See the formula, worked examples, conversion table, history, and common uses.
Femtowatts to Watts converter
Converter
Power Converter
Convert watts, horsepower, refrigeration tons, BTU per hour, and engineering power units.
Context values
Some unit families need one extra value for a physically accurate result.
The watt is one joule per second.
Result = input x 1e-15 / 1.
Power uses the watt as the base unit.
Reserved above the conversion cards and below the converter.
About Converting Femtowatts to Watts
Femtowatt and Watt both describe power output, and the conversion is a routine part of comparing an engine or motor's spec sheet across countries that use different power units. Specifically: Femtowatt is 1e-15 watt units, and the watt is one joule per second.
Formula
watts = femtowatts × 1e-15
This factor comes from each unit's defined relationship to the category's base unit: 1 femtowatt equals 1e-15 base units, and 1 watt equals 1 base unit, so dividing one by the other gives the direct femtowatt-to-watt factor of 1e-15.
Simple example
1 fW × 1e-15 = 1e-15 W
1 femtowatt = 1e-15 watts.
Real-world example
100 fW × 1e-15 = 1e-13 W
100 femtowatts = 1e-13 watts.
Conversion table
| Femtowatt (fW) | Watt (W) |
|---|---|
| 1 fW | 1e-15 W |
| 10 fW | 1e-14 W |
| 100 fW | 1e-13 W |
| 500 fW | 5e-13 W |
| 1,000 fW | 1e-12 W |
| 5,000 fW | 5e-12 W |
Reverse conversion: Watt to Femtowatt
1e-15 W × 1e+15 = 1 fW
1e-15 watts = 1 femtowatt.
femtowatts = watts × 1e+15
For a page dedicated to this direction, see Watt to Femtowatt.
Understanding the Femtowatt (fW)
Femtowatt is 1e-15 watt units.
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.
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 watts are in 1 femtowatt?
1 femtowatt equals 1e-15 watts, using the exact defined conversion factor rather than an estimate.
How do I convert femtowatt to watt?
Multiply the femtowatt value by 1e-15. The converter above does this instantly to whatever precision you set.
How do I convert watt back to femtowatt?
Use the reverse factor: 1 watt equals 1e+15 femtowatts. You can also use the swap control in the converter above to flip the direction instantly.
What is a femtowatt?
Femtowatt (fW) is a unit of power.
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.
Is the femtowatt to watt conversion exact?
Yes. Both femtowatt and watt 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.