The watt is one joule per second.
Watts to Horsepowers Converter — W to hp
Convert Watt (W) to Horsepower (hp) using the exact conversion factor (1 watt = 0.0013410221 horsepower). See the formula, worked examples, conversion table, unit comparison, history, and common uses.
Watts 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 1 / 745.6998716.
Power uses the watt as the base unit.
Reserved above the conversion cards and below the converter.
About Converting Watts to Horsepowers
Watt 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. Watt is typically associated with standard scientific and everyday power unit worldwide, while Horsepower is typically associated with united States and United Kingdom (vehicle and engine specifications).
Formula
horsepowers = watts × 0.0013410220896
This factor comes from each unit's defined relationship to the category's base unit: 1 watt equals 1 base unit, and 1 horsepower equals 745.699871582 base units, so dividing one by the other gives the direct watt-to-horsepower factor of 0.0013410220896.
Simple example
1 W × 0.00134102209 = 0.0013410221 hp
1 watt = 0.0013410221 horsepowers.
Real-world example
100 W × 0.00134102209 = 0.134102209 hp
100 watts = 0.134102209 horsepowers.
Conversion table
| Watt (W) | Horsepower (hp) |
|---|---|
| 1 W | 0.0013410221 hp |
| 10 W | 0.0134102209 hp |
| 100 W | 0.134102209 hp |
| 500 W | 0.6705110448 hp |
| 1,000 W | 1.34102209 hp |
| 5,000 W | 6.705110448 hp |
Reverse conversion: Horsepower to Watt
0.0013410221 hp × 745.6998716 = 1.000000008 W
0.0013410221 horsepowers = 1.000000008 watts.
watts = horsepowers × 745.699871582
For a page dedicated to this direction, see Horsepower to Watt.
Watt vs. Horsepower
| Aspect | Watt | Horsepower |
|---|---|---|
| Family | SI derived unit | US/imperial customary unit |
| Typical use | Electrical appliance power ratings worldwide | US and UK vehicle engine power ratings |
| Where it's used | Standard scientific and everyday power unit worldwide | United States and United Kingdom (vehicle and engine specifications) |
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 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.
Watt — sources
- BIPM SI Brochure — Coherent derived units — Defines the watt as the SI unit of power.
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 watt?
1 watt equals 0.0013410221 horsepowers, using the exact defined conversion factor rather than an estimate.
How do I convert watt to horsepower?
Multiply the watt value by 0.00134102209. The converter above does this instantly to whatever precision you set.
How do I convert horsepower back to watt?
Use the reverse factor: 1 horsepower equals 745.6998716 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 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 watt 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.
Where is the watt still used today?
Standard scientific and everyday power unit worldwide