Watts to Horsepower (W to hp)
1 watt equals 0.00134102209 horsepower (rounded).
How to convert watts to horsepower
To convert watts to horsepower, multiply the number of watts by 0.00134102209. The factor is rounded to 10 significant digits. To go the other way, multiply horsepower by 745.6998716 (rounded).
horsepower = watts × 0.00134102209
Example: 10 watts = 0.0134102209 horsepower.
Several different horsepower units exist. This site lists mechanical (745.7 W), metric (735.5 W) and electrical (746 W) horsepower separately.
About these units
Watt (W)
The SI unit of power: one joule per second. A typical LED bulb uses 5–10 W and a laptop 30–60 W.
Credit for the name goes to C. William Siemens, who proposed it in August 1882 in his presidential address to the British Association for the Advancement of Science. He chose it to honor James Watt, the Scottish inventor who in 1776 improved the Newcomen steam engine. An International Conference on Electric Units and Standards adopted Siemens' definition in London in October 1908 as the international watt. After the 1948 General Conference on Weights and Measures the unit was redefined in absolute terms, and in 1960 the 11th General Conference adopted it into the SI as the unit of power.
Today one watt is one joule per second, or equivalently one volt times one ampere. Orders-of-magnitude tables put an LED light bulb at about 7 W and an adult's basal metabolic rate at roughly 100 W. A 100 kg person climbing a 3 m ladder in 5 seconds works at about 600 W, while a laborer can sustain around 75 W over an eight-hour day. The watt measures a rate, so it says how fast energy is being used, not how much has been used in total.
The watt is the reference unit for power on this site.
Sources: Wikipedia: Watt; Wikipedia: Orders of magnitude (power)
Horsepower (hp)
The mechanical horsepower: 550 foot-pounds per second, about 745.7 watts. James Watt coined it to compare steam engines with draft horses.
Horsepower was a sales pitch before it was a unit. Late in the 18th century the Scottish engineer James Watt adopted the term to compare the output of steam engines with the draft horses they replaced. His 1782 experiments found that a brewery horse could produce 32,400 foot-pounds-force per minute, and in 1783 he and Matthew Boulton standardized the figure at 33,000 foot-pounds-force per minute. Customers could then be told how many horses an engine would replace.
That figure works out to 550 foot-pounds-force per second, or about 745.7 watts: the power needed to lift 550 pounds by one foot in one second. Several cousins exist, including metric horsepower and electrical horsepower, defined as exactly 746 W. Car ratings added more confusion. Early British taxable horsepower was a formula based on bore and cylinder count, not measured output, and American ratings before 1972 used SAE gross brake horsepower, measured without accessories. In the European Union, horsepower may be used only as a supplementary unit under Directive 80/181/EEC, in force from 1 January 2010.
1 horsepower = 745.6998716 watts (approximately).
Sources: Wikipedia: Horsepower; Wikipedia: Metric horsepower
Related conversions
- Horsepower to watts (reverse)
- Watts to kilowatts
- Watts to megawatts
- Watts to gigawatts
- Watts to metric horsepower
- Watts to BTU per hour
- Watts to milliwatts
- Watts to electrical horsepower
- Watts to foot-pounds per second
- Watts to tons of refrigeration
- Watts to kilocalories per hour
- Watts to calories per second
- Watts to ergs per second
- Kilowatts to horsepower
- Megawatts to horsepower
- Gigawatts to horsepower
- Metric horsepower to horsepower
- BTU per hour to horsepower
- Milliwatts to horsepower
- Electrical horsepower to horsepower
- Foot-pounds per second to horsepower
- Tons of refrigeration to horsepower
- Kilocalories per hour to horsepower
- Calories per second to horsepower
- Ergs per second to horsepower
See all power units.