Horsepower to Kilowatts (HP to kW) Converter

The Horsepower to Kilowatts (HP to kW) Converter provides an accurate and fast way to translate power ratings between the imperial horsepower unit and the SI metric kilowatt. This conversion is one of the most frequently needed in electrical engineering, motor selection, HVAC system design, automotive engineering, and industrial equipment specification — any time equipment rated in horsepower must be compared to or integrated with systems specified in kilowatts.

The term horsepower was coined by the Scottish engineer James Watt in the late 18th century to market his improved steam engines. By comparing his engine's output to the work a draft horse could sustain over time, Watt arrived at approximately 33,000 foot-pounds of work per minute (550 foot-pounds per second), which became the definition of mechanical horsepower. This unit dominated English-speaking engineering for over two centuries and remains deeply embedded in motor nameplates, vehicle specifications, and equipment catalogs worldwide.

The kilowatt, defined as 1000 watts (joules per second), is the SI unit of power and is universally used in scientific, industrial, and commercial contexts outside North America. The International Electrotechnical Commission (IEC) and most national electrical codes outside the US specify motor ratings in kilowatts, making conversion between HP and kW an everyday necessity for engineers working across international standards.

There are actually four distinct definitions of horsepower, each with a slightly different kilowatt equivalent:

• Mechanical (Imperial) HP: 550 ft·lbf/s = 745.69987 W ≈ 0.7457 kW. This is the most common definition in US engineering and motor ratings.
• Metric HP (PS / CV / pk): 75 kgf·m/s = 735.49875 W ≈ 0.73550 kW. Used in European automotive engineering — a European car's "75 PS" engine produces 75 metric horsepower, not 75 mechanical HP.
• Electrical HP: Exactly 746 W = 0.746 kW. Defined by the US National Electrical Code for electric motor rating purposes. Very close to mechanical HP but slightly higher.
• Boiler HP: 9.8095 kW (the heat required to evaporate 34.5 pounds of water per hour from 212°F). Used almost exclusively for steam boiler sizing and is far larger than the other definitions.

For most electrical and mechanical engineering work, mechanical HP (0.7457 kW) is the correct conversion factor. When reading European automotive specifications or selecting motors for European markets, use metric HP (0.73550 kW). When referencing NEC motor nameplate ratings and ampacity tables, use electrical HP (0.746 kW).

Practical conversion examples across industries: a 100 HP industrial motor draws approximately 74.6 kW at full load; a 200 HP diesel generator produces about 149 kW of electrical output; a 5 HP residential well pump requires roughly 3.73 kW from the supply circuit; a 400 HP commercial HVAC chiller compressor demands approximately 298 kW. These numbers are critical for correctly sizing conductors, overcurrent protection, transformers, and generator capacity under NEC Article 430 and related standards.

This converter displays results in kW, W, and MW simultaneously, making it convenient for applications ranging from small fractional-horsepower motors (where watts is the most meaningful unit) to large utility-scale machinery (where megawatts provides the best perspective). Always select the correct horsepower type for your application to ensure accurate electrical system design.