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Horsepower Conversion Table
This comprehensive horsepower conversion table shows how various units relate to horsepower. Use this reference for quick conversions between horsepower and other common power units.
| Conversion | To Unit | Multiplier |
|---|---|---|
| Horsepower to watts | Watts | 745.7 (mechanical) / 735.5 (metric) |
| Horsepower to kilowatts | Kilowatts | 0.7457 (mechanical) / 0.7355 (metric) |
| Horsepower to megawatts | Megawatts | 0.0007457 (mechanical) / 0.0007355 (metric) |
| Horsepower to BTU/h | BTU/h | 2544.43 (mechanical) / 2509.63 (metric) |
| Horsepower to tons of refrigeration | Tons of Refrigeration | 0.212 (mechanical) / 0.209 (metric) |
This horsepower conversion reference table provides accurate conversion factors for both mechanical horsepower (hp) and metric horsepower (hp). All values are based on internationally recognized standards for maximum precision in engineering and scientific applications.
What is Horsepower?
Horsepower (hp) is a unit of power that was originally defined by James Watt in the late 18th century to compare the output of steam engines with the power of draft horses. One mechanical horsepower is defined as approximately 745.7 watts, while one metric horsepower is defined as exactly 735.5 watts.
Horsepower is commonly used to express the maximum power of engines, especially in the automotive and marine industries. Our horsepower conversion tool helps you easily convert between horsepower and other units like watts, kilowatts, and BTUs. For example, 100 mechanical horsepower equals approximately 74.57 kilowatts.
Types of Horsepower
There are several definitions of horsepower, with the most common being mechanical horsepower (also known as imperial horsepower) and metric horsepower:
- Mechanical horsepower (hp) = 745.7 watts
- Metric horsepower (hp) = 735.5 watts
- Boiler horsepower = 9812.5 watts (used for boiler output)
- Electrical horsepower = 746 watts (used for electric motors)
- Hydraulic horsepower = varies with pressure and flow rate
What is Horsepower Used For?
Horsepower is used in a wide range of applications where power measurement is needed. It's particularly common in the automotive industry, marine propulsion, and industrial machinery:
Automotive Industry
Engine power ratings for cars, trucks, and motorcycles. For example, a typical compact car might have 120 horsepower while a sports car could have 400+ horsepower.
Marine Propulsion
Engine power for boats, ships, and yachts. Small boats might have 50-100 horsepower engines while large ships can have engines exceeding 100,000 horsepower.
Industrial Machinery
Power ratings for pumps, compressors, and manufacturing equipment. For example, a large industrial pump might require a 200 horsepower motor.
Aerospace
Jet engine thrust and helicopter power requirements. A commercial airliner might have engines producing 50,000+ horsepower equivalent.
Etymology and History
The term "horsepower" was coined by Scottish engineer James Watt in the late 1700s. Watt needed a way to market his improved steam engines by comparing their power output to something people could understand - the work done by draft horses.
Watt's definition was based on his observations of brewery horses working at a mill. He estimated that a horse could turn a mill wheel 144 times in an hour (or 2.4 times a minute) with a 12-foot radius wheel, which he calculated to be about 33,000 foot-pounds of work per minute. This became the standard for mechanical horsepower.
Metric horsepower was later defined as exactly 75 kilogram-force meters per second (kgf·m/s), which equals approximately 735.5 watts. This definition is slightly different from mechanical horsepower and is commonly used in Europe.
Frequently Asked Questions
What is the difference between mechanical and metric horsepower?
Mechanical horsepower (also known as imperial horsepower) is defined as exactly 745.7 watts, while metric horsepower is defined as exactly 735.5 watts. The difference is about 1.4%. When converting horsepower, it's important to know which definition is being used, as it will affect your results.
How accurate is the horsepower definition?
The modern definitions of both mechanical and metric horsepower are precisely defined in terms of watts, making them highly accurate. Mechanical horsepower is exactly 745.7 watts and metric horsepower is exactly 735.5 watts. These definitions make horsepower conversion straightforward and precise.
Why do car manufacturers use horsepower?
Horsepower provides a familiar way for consumers to understand engine performance. Since people have long associated power with horses, the unit makes engine capabilities more relatable than raw technical specifications. It's also a traditional unit in the automotive industry.
How do I convert horsepower to other units?
Use our horsepower conversion calculators above, or multiply by the appropriate conversion factor. For example, to convert mechanical horsepower to watts, multiply by 745.7; to convert metric horsepower to kilowatts, multiply by 0.7355. For detailed instructions, visit our specific converter pages.
What are common uses for horsepower conversion?
Horsepower conversion is essential in automotive engineering, marine propulsion, industrial equipment selection, and HVAC system design. Whether calculating engine specifications or determining electrical requirements for machinery, our horsepower converter tool simplifies these tasks.
How does horsepower conversion differ from other power units?
Horsepower is a traditional unit that's still widely used, especially in the automotive industry, while watts and kilowatts are SI units. Horsepower conversion involves specific conversion factors (745.7 for mechanical, 735.5 for metric) rather than powers of ten like other SI conversions.
Can I convert very small or very large horsepower measurements?
Yes, our horsepower converter handles both extremely small and large measurements with precision. For tiny power measurements, you might convert millihorsepower to watts. For large industrial applications, you can convert thousands of horsepower to megawatts. Our smart rounding feature ensures readable results.
Is your horsepower conversion tool free to use?
Yes, our horsepower conversion calculator is completely free with no registration required. Simply enter your value, select your target unit, and get instant, accurate results. We believe precise power conversion should be accessible to everyone, from students to professionals.