Convert Mechanical Horsepower to Watt (hp → W)

Converting mechanical horsepower to watts is straightforward: multiply by the conversion factor. Follow these three steps to do it by hand or in your head.

1. 1
   Take your value in mechanical horsepower

   Start with the number of mechanical horsepower (hp) you want to convert.
2. 2
   Multiply by 745.69987

   The conversion factor from hp to W is 745.69987. Multiply your value by this number.
3. 3
   Read the result in watts

   The result is your value in watts (W).

Multiply the value in mechanical horsepower by 745.69987. For the reverse direction, multiply by 0.001341.

• ✓1 hp = 745.7 W = 0.7457 kW.
• ✓US car ads quote hp; European ads quote kW or PS.
• ✓Metric horsepower (PS) differs by ~1.4% — be aware.

• ✗Assuming hp and PS are identical — 1.4% difference.
• ✗Using horsepower for electrical devices — watts more appropriate.
• ✗Confusing horsepower at engine flywheel vs wheel (transmission losses).

What is the Mechanical Horsepower?

Horsepower (hp) equals exactly 745.6998715822702 watts (mechanical horsepower) and is the American and British unit for car engines, motorcycles, motorboats, and traditional mechanical power ratings. James Watt invented the unit in the 1780s to market his steam engines: he calculated that a brewery horse could continuously turn a mill wheel at 33,000 ft·lb per minute, which became 1 horsepower. American cars typically range from 150 hp (economy) to 700 hp (sports cars), pickup trucks 250–500 hp, and large diesel trucks 400–600 hp. Outside the US, the metric horsepower (PS or CV, equal to 735.5 W — about 1.4% smaller than mechanical hp) is sometimes used. Horsepower relates to the watt (1 hp ≈ 745.7 W), the kilowatt (1 hp ≈ 0.746 kW), and the metric horsepower (1 hp ≈ 1.014 PS). Despite SI's preference for the watt, horsepower remains entrenched in automotive marketing.

• US car and motorcycle engine ratings
• Lawn mower and small engine specs
• US pump and compressor ratings

What is the Watt?

The watt is the SI unit of power, equal to one joule per second (1 W = 1 J/s). Named after Scottish engineer James Watt (1736–1819), whose improvements to the steam engine sparked the Industrial Revolution, the watt unifies mechanical, electrical, and thermal power. A typical LED bulb consumes 8–12 W to produce as much light as a 60-W incandescent bulb. Human resting metabolism is about 80–100 W of heat output, while peak athletic performance reaches 400–1,500 W (briefly). The watt is fundamental in electrical engineering: P = V × I (power = voltage × current). It relates to the kilowatt (1 kW = 1,000 W), the megawatt (1 MW = 10⁶ W), horsepower (1 hp ≈ 745.7 W), and the BTU per hour (1 W ≈ 3.412 BTU/h). Light bulb and appliance ratings, electric motor outputs, and audio amplifier specifications all use the watt as the base unit.

• Light-bulb and appliance ratings
• Scientific and engineering power specs
• Radio and electronics power