What is watt?

The watt is the SI base unit of power. It is universally used to measure the rate of energy consumption or production in electrical appliances, engines, lighting, and virtually all power-related specifications.

Real-world uses

The watt is the SI unit of power, used to rate electrical appliances (a kettle is about 2,000 W, an LED bulb 8–12 W), solar panels, audio amplifiers, and motors. Electricity generation at power stations and renewable installations is measured in watts and its multiples.

History

Named after Scottish engineer James Watt (1736–1819), the unit was adopted by the Second Congress of the British Association for the Advancement of Science in 1882. Watt's improvements to the steam engine were foundational to the Industrial Revolution.

Common mistakes

Confusing watts (power) with watt-hours (energy). A 100 W light bulb uses 100 watt-hours of energy per hour. Also, equating wattage with brightness for LED bulbs—lumens measure brightness, watts measure power consumption.

What is horsepower (mechanical)?

Mechanical horsepower is a traditional unit of power equal to approximately 745.7 watts. It is widely used in automotive and industrial contexts to express engine output, pump capacity, and motor ratings.

Real-world uses

Horsepower is used to rate car engines, industrial motors, lawn mowers, outboard boat motors, and air compressors in the United States and some other markets. A typical family car engine ranges from 100–300 hp. It is also used in aviation and marine propulsion ratings.

History

James Watt coined the term "horsepower" around 1782 to help customers understand the power of his steam engines by comparing it to draft horses. He calculated that a horse could perform work at a rate of about 33,000 foot-pounds per minute, which became the definition of one mechanical horsepower.

Common mistakes

There are at least three different definitions: mechanical horsepower (approximately 745.7 W), metric horsepower (735.5 W), and electrical horsepower (746 W). Automotive specifications often do not specify which type is used, and the differences matter when comparing international specifications.

When is this conversion used?

Converting between watt and horsepower (mechanical) is common when working across metric and imperial systems, such as international trade, travel between countries with different measurement standards, or following instructions from a different region.

Worked examples

1 watt = 0.00134102 horsepower (mechanical)

1 horsepower (mechanical) = 745.69987158 watt

How to convert watt to horsepower (mechanical)

To convert watt to horsepower (mechanical), multiply the value by 0.00134102.

To convert horsepower (mechanical) back to watt, multiply by 745.69987158.

Measurement standards

The watt is the SI derived unit of power, defined as one joule per second (kg·m²/s³). Horsepower remains in widespread informal use, particularly in the automotive industry, but has no single universal definition across regions.

Did you know?

The human body at rest produces about 80 watts of power — roughly enough to keep an incandescent light bulb glowing. During intense exercise, a trained cyclist can sustain over 400 watts, and elite sprinters briefly exceed 2,000 watts.

Quick reference: watt to horsepower (mechanical)

watt	horsepower (mechanical)
0.1	0.0001341
0.5	0.00067051
1	0.00134102
2	0.00268204
5	0.00670511
10	0.01341022
25	0.03352555
50	0.0670511
100	0.13410221
250	0.33525552
500	0.67051104
1,000	1.34102209

Common values

	watt	horsepower (mechanical)
LED light bulb	10 watt	0.01341022 horsepower (mechanical)
Desktop computer	300 watt	0.40230663 horsepower (mechanical)
Microwave oven	1,000 watt	1.34102209 horsepower (mechanical)
Small car engine	75,000 watt	100.57665672 horsepower (mechanical)
Wind turbine (large)	3,000,000 watt	4,023.06626879 horsepower (mechanical)

Available Power units

More watt conversions

Assumption: horsepower values use mechanical horsepower.