Femtowatt is 1e-15 watt units.
Femtowatts to Horsepowers Converter — fW to hp
Convert Femtowatt (fW) to Horsepower (hp) using the exact conversion factor (1 femtowatt = 1.341022e-18 horsepower). See the formula, worked examples, conversion table, history, and common uses.
Femtowatts to Horsepowers 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.
Mechanical horsepower.
Result = input x 1e-15 / 745.6998716.
Power uses the watt as the base unit.
Reserved above the conversion cards and below the converter.
About Converting Femtowatts to Horsepowers
Femtowatt and Horsepower 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 mechanical horsepower.
Formula
horsepowers = femtowatts × 1.341022e-18
This factor comes from each unit's defined relationship to the category's base unit: 1 femtowatt equals 1e-15 base units, and 1 horsepower equals 745.699871582 base units, so dividing one by the other gives the direct femtowatt-to-horsepower factor of 1.341022e-18.
Simple example
1 fW × 1.341022e-18 = 1.341022e-18 hp
1 femtowatt = 1.341022e-18 horsepowers.
Real-world example
100 fW × 1.341022e-18 = 1.341022e-16 hp
100 femtowatts = 1.341022e-16 horsepowers.
Conversion table
| Femtowatt (fW) | Horsepower (hp) |
|---|---|
| 1 fW | 1.341022e-18 hp |
| 10 fW | 1.341022e-17 hp |
| 100 fW | 1.341022e-16 hp |
| 500 fW | 6.70511e-16 hp |
| 1,000 fW | 1.341022e-15 hp |
| 5,000 fW | 6.70511e-15 hp |
Reverse conversion: Horsepower to Femtowatt
1.341022e-18 hp × 7.456999e+17 = 0.9999999332 fW
1.341022e-18 horsepowers = 0.9999999332 femtowatts.
femtowatts = horsepowers × 7.456999e+17
For a page dedicated to this direction, see Horsepower to Femtowatt.
Understanding the Femtowatt (fW)
Femtowatt is 1e-15 watt units.
Understanding the Horsepower
Horsepower (hp) measures power. Mechanical horsepower is defined as exactly 745.6998715822702 watts. It is classified as a US/imperial customary unit.
Where it's used: United States and United Kingdom (vehicle and engine specifications)
Mechanical horsepower vs. metric horsepower. Mechanical horsepower (745.7 W) and metric horsepower/PS (735.5 W) differ by about 1.4% — a US car spec sheet in 'hp' and a European one in 'PS' are not directly comparable numbers without conversion.
Uses of the Horsepower today
- US and UK vehicle engine power ratings
- Motor and engine specifications in English-speaking markets
History of the Horsepower
James Watt popularized horsepower in the 1780s as a marketing figure, comparing his steam engines' output to the working capacity of a horse (based on his estimate of a horse turning a mill), so buyers could grasp engine capability in familiar terms. The unit stuck long after its origin as a sales tool, eventually being formally defined at exactly 550 foot-pounds per second.
Historical origin. Horsepower was not the invention of a single named person; it developed through the process described above.
Horsepower — sources
- NIST Special Publication 811 — Documents the exact watt-equivalence of mechanical horsepower.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many horsepowers are in 1 femtowatt?
1 femtowatt equals 1.341022e-18 horsepowers, using the exact defined conversion factor rather than an estimate.
How do I convert femtowatt to horsepower?
Multiply the femtowatt value by 1.341022e-18. The converter above does this instantly to whatever precision you set.
How do I convert horsepower back to femtowatt?
Use the reverse factor: 1 horsepower equals 7.456999e+17 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 horsepower?
Horsepower (hp) measures power. Mechanical horsepower is defined as exactly 745.6998715822702 watts. It is classified as a US/imperial customary unit.
Is the femtowatt to horsepower conversion exact?
Yes. Mechanical horsepower is defined as exactly 745.6998715822702 watts. That fixed definition is what the converter above uses, so any rounding you see is a display choice, not a limitation of the math.
What is the difference between mechanical horsepower vs. metric horsepower?
Mechanical horsepower (745.7 W) and metric horsepower/PS (735.5 W) differ by about 1.4% — a US car spec sheet in 'hp' and a European one in 'PS' are not directly comparable numbers without conversion.