Mechanical horsepower.
Horsepowers to Watts Converter — hp to W
Convert Horsepower (hp) to Watt (W) using the exact conversion factor (1 horsepower = 745.6998716 watt). See the formula, worked examples, conversion table, unit comparison, history, and common uses.
Horsepowers to Watts 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.
The watt is one joule per second.
Result = input x 745.6998716 / 1.
Power units are compatible.
Reserved above the conversion cards and below the converter.
About Converting Horsepowers to Watts
Horsepower and Watt 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. Horsepower is typically associated with united States and United Kingdom (vehicle and engine specifications), while Watt is typically associated with standard scientific and everyday power unit worldwide.
Formula
watts = horsepowers × 745.699871582
This factor comes from each unit's defined relationship to the category's base unit: 1 horsepower equals 745.699871582 base units, and 1 watt equals 1 base unit, so dividing one by the other gives the direct horsepower-to-watt factor of 745.699871582.
Simple example
1 hp × 745.6998716 = 745.6998716 W
1 horsepower = 745.6998716 watts.
Real-world example
100 hp × 745.6998716 = 74,569.98716 W
100 horsepowers = 74,569.98716 watts.
Conversion table
| Horsepower (hp) | Watt (W) |
|---|---|
| 1 hp | 745.6998716 W |
| 10 hp | 7,456.998716 W |
| 50 hp | 37,284.99358 W |
| 100 hp | 74,569.98716 W |
| 500 hp | 372,849.9358 W |
| 1,000 hp | 745,699.8716 W |
Reverse conversion: Watt to Horsepower
745.6998716 W × 0.00134102209 = 1 hp
745.6998716 watts = 1 horsepowers.
horsepowers = watts × 0.0013410220896
For a page dedicated to this direction, see Watt to Horsepower.
Horsepower vs. Watt
| Aspect | Horsepower | Watt |
|---|---|---|
| Family | US/imperial customary unit | SI derived unit |
| Typical use | US and UK vehicle engine power ratings | Electrical appliance power ratings worldwide |
| Where it's used | United States and United Kingdom (vehicle and engine specifications) | Standard scientific and everyday power unit worldwide |
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.
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.
Horsepower — sources
- NIST Special Publication 811 — Documents the exact watt-equivalence of mechanical horsepower.
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 horsepower?
1 horsepower equals 745.6998716 watts, using the exact defined conversion factor rather than an estimate.
How do I convert horsepower to watt?
Multiply the horsepower value by 745.6998716. The converter above does this instantly to whatever precision you set.
How do I convert watt back to horsepower?
Use the reverse factor: 1 watt equals 0.0013410221 horsepowers. You can also use the swap control in the converter above to flip the direction instantly.
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.
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 horsepower to watt 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 horsepower still used today?
United States and United Kingdom (vehicle and engine specifications)