Horsepower to Watts Converter

Relationship Between Horsepower and Watt

The conversion between horsepower (hp) and watt (W) is a fundamental power unit conversion between imperial and metric systems.

1 hp = 745.699872 W

Therefore,

1 W = 0.00134102 hp

To convert horsepower to watts, we multiply the value in horsepower by 745.699872.

For example, 1 hp equals approximately 745.7 W, which is the standard mechanical horsepower. A common automotive engine producing 150 hp is equivalent to approximately 111,855 W (111.855 kW).

Quick Reference:
Horsepower is commonly used in the automotive, marine, and industrial sectors, especially in the United States. The watt is the standard SI unit used worldwide. Understanding horsepower to watt conversion is essential for working with engines, motors, and power systems across different measurement standards.

Horsepower (hp)

What is Horsepower?

Horsepower (symbol: hp) is a unit of power in the imperial and US customary systems. It was originally defined by James Watt to compare the output of steam engines with the power of draft horses. Today, mechanical horsepower is defined as exactly 745.699872 watts, making it a convenient unit for measuring engine and motor power.

Historical Background

Horsepower was developed by James Watt in the late 18th century to market his steam engines. He calculated that a horse could turn a mill wheel 144 times in an hour (or 2.4 times a minute), and the wheel was 12 feet in radius. This led to the definition of 1 horsepower as the ability to lift 550 pounds by 1 foot in 1 second, which equals 33,000 foot-pounds per minute or approximately 745.7 watts.

Types of Horsepower

• Mechanical horsepower (hp): The standard definition, equal to 745.699872 W, commonly used in the United States and United Kingdom
• Metric horsepower (PS): Used in Europe, equal to 735.49875 W (slightly different from mechanical hp)
• Electric horsepower: Equal to 746 W, used for electric motors
• Boiler horsepower: Used for steam boilers, equal to 33,475 BTU/h or approximately 9,809.5 W
• Hydraulic horsepower: Used in hydraulic systems, calculated based on pressure and flow rate

Common Applications

• Automotive: Car engines (100-700 hp typical), trucks (200-600 hp), motorcycles (50-200 hp)
• Marine: Boat engines (50-5000 hp), outboard motors (5-450 hp)
• Industrial: Manufacturing equipment, pumps, compressors (1-1000 hp)
• Agricultural: Tractors (20-500 hp), combines, farm equipment
• Aircraft: Small aircraft engines (100-400 hp), large aircraft (thousands of hp)
• Construction: Heavy machinery, excavators, bulldozers (50-1000 hp)
• Power tools: Large industrial tools, generators
• Racing: High-performance vehicles (300-1500+ hp)
• Marine propulsion: Ship engines (hundreds to thousands of hp)
• Power generation: Backup generators, portable generators (1-500 hp)

Horsepower Standards

In the United States and United Kingdom, mechanical horsepower (hp) is the standard unit for engine and motor ratings. Understanding horsepower to watt conversion is essential for comparing power ratings across different systems, especially when working with international standards or converting between metric and imperial units.

Watt (W)

What is a Watt?

The watt (symbol: W) is the unit of power in the International System of Units (SI). It is defined as one joule per second (1 W = 1 J/s) and represents the rate at which energy is transferred or converted. The watt is named after Scottish inventor James Watt, who made significant contributions to the development of the steam engine.

SI Base Unit

As the base unit of power, the watt is part of the globally standardized metric system. 1 W = 1 J/s = 1 kg·m²/s³. This coherent system makes scientific calculations straightforward and eliminates conversion errors. The watt is used worldwide for measuring power in electrical, mechanical, and thermal systems.

Common Applications

• Household appliances: Light bulbs (40-100 W), refrigerators (100-800 W), washing machines (500-2000 W)
• Electronics: Laptop computers (30-100 W), desktop computers (200-500 W), televisions (50-400 W)
• Electric motors: Small motors (100-500 W), industrial motors (1-100 kW and higher)
• Power generation: Solar panels (200-400 W per panel), wind turbines (1-5 MW)
• Heating systems: Electric heaters (1000-3000 W), heat pumps (2000-5000 W)
• HVAC systems: Air conditioners (1000-5000 W), fans (50-200 W)
• Kitchen appliances: Microwaves (600-1200 W), toasters (800-1500 W), coffee makers (800-1200 W)
• Lighting: LED bulbs (5-20 W), fluorescent tubes (15-40 W), incandescent bulbs (40-100 W)
• Power tools: Drills (500-1500 W), saws (1000-2000 W), sanders (300-800 W)
• Automotive: Car alternators (500-2000 W), electric vehicle motors (50-300 kW)

Practical Values

Common power values in watts provide easy-to-remember reference points: Standard light bulb ≈ 60-100 W; Laptop computer ≈ 50 W; Desktop computer ≈ 200 W; Refrigerator ≈ 100-200 W; Microwave oven ≈ 1000 W; Electric water heater ≈ 3000-5000 W. The watt's range makes it ideal for measuring power consumption of everyday devices.

Conversion Benefits

Understanding horsepower to watt conversion enables seamless work across power measurements in different unit systems. Horsepower is commonly used for engine and motor ratings, especially in automotive and industrial applications, while watts are used worldwide in electrical and scientific contexts.

Horsepower to Watt Conversion Table

Common horsepower to watt conversions for reference: