HP to Watts Converter

Horsepower (HP)	Watts (W)
0.5 HP	373 W
1 HP	746 W
2 HP	1,491 W
5 HP	3,729 W
10 HP	7,457 W
25 HP	18,643 W
50 HP	37,285 W
100 HP	74,570 W
200 HP	149,140 W

Complete Guide: Converting Horsepower to Watts

Converting horsepower (HP) to watts is fundamental in electrical engineering, automotive, and industrial applications. This comprehensive guide explains the conversion process, formula, and practical applications of HP to watts conversion.

Understanding the Conversion

Horsepower is a traditional unit of power developed by James Watt in the 18th century, while watts are the standard SI unit of power named after the same inventor. The conversion is based on the precise definition of mechanical horsepower.

Conversion Formula

The conversion from horsepower to watts uses the following formula:

Watts = HP × 745.699872

For practical purposes, we often round this to 745.7, which provides sufficient accuracy for most applications.

Historical Background

James Watt defined horsepower as the power needed to lift 550 pounds one foot in one second. This translates to:

1 HP = 550 foot-pounds per second
1 HP = 33,000 foot-pounds per minute
1 HP = 745.699872 watts (exact)
1 HP = 0.745699872 kilowatts

Types of Horsepower

Different standards exist for horsepower:

Mechanical HP: 745.7 watts (US standard)
Metric HP (PS): 735.5 watts (European standard)
Electrical HP: 746 watts (exact electrical definition)
Boiler HP: 9,810 watts (steam generation)

Common Applications

Electric Motors: Converting mechanical ratings to electrical consumption
Automotive: Engine power specifications and electric vehicle motors
Industrial Equipment: Power tools, compressors, and machinery
HVAC Systems: Fan motors, compressors, and pumps
Marine Applications: Boat engines and electric propulsion

Practical Examples

Drill motor: 0.5 HP = 373 watts
Table saw: 3 HP = 2,237 watts
Air compressor: 5 HP = 3,729 watts
Car engine: 200 HP = 149,140 watts
Industrial pump: 50 HP = 37,285 watts

Electrical Considerations

When converting HP to watts for electrical applications:

Motor Efficiency: Electric motors are 80-95% efficient
Power Factor: AC motors may have reactive power components
Starting Current: Motors draw more power during startup
Load Variations: Actual power consumption varies with load

Tips for Accurate Conversion

Specify which type of horsepower you're using
Use the precise factor (745.699872) for engineering calculations
Consider motor efficiency when calculating electrical requirements
Account for power factor in AC electrical systems
Include safety margins for electrical system design

Frequently Asked Questions

Why is 1 HP equal to 745.7 watts?

This comes from James Watt's definition of horsepower as 550 foot-pounds per second, which when converted to the metric system equals exactly 745.699872 watts.

Does a 1 HP motor consume exactly 745.7 watts?

Not exactly. The conversion gives equivalent power output. Due to efficiency losses, a 1 HP motor typically consumes 800-900 watts of electrical power to produce 745.7 watts of mechanical power.

Can I use this conversion for all types of horsepower?

This conversion is for mechanical horsepower. Metric HP (PS) converts to 735.5 watts. Always verify which standard is being used in your application.

How do I size electrical circuits for HP motors?

Convert HP to watts, then divide by efficiency (typically 0.85-0.95) and voltage to get current requirements. Add safety margins per electrical codes.

What's the difference between continuous and peak HP ratings?

Continuous HP is sustainable power output, while peak HP is maximum short-term output. For electrical sizing, use continuous ratings plus appropriate safety factors.

Conversion Result

HP to Watts Conversion Table

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