## Horsepower |

**Horsepower** (**hp**) is a unit of measurement of **mechanical horsepower** (or **imperial horsepower**), which is about 745.7 **metric horsepower**, which is approximately 735.5 watts.

The term was adopted in the late 18th century by ^{[1]}^{[2]} The definition of the unit varied among geographical regions. Most countries now use the * watt* for measurement of power. With the implementation of the EU Directive

- history
- calculating power
- definitions
- measurement
- engine power test standards
- see also
- references
- external links

The development of the *The Miner's Friend*:

So that an engine which will raise as much water as two horses, working together at one time in such a work, can do, and for which there must be constantly kept ten or twelve horses for doing the same. Then I say, such an engine may be made large enough to do the work required in employing eight, ten, fifteen, or twenty horses to be constantly maintained and kept for doing such a work…

^{[4]}

The idea was later used by ^{[5]} This royalty scheme did not work with customers who did not have existing steam engines but used horses instead.

Watt determined that a horse could turn a ^{[6]} The wheel was 12 feet (3.7 m) in radius; therefore, the horse travelled 2.4 × 2π × 12 feet in one minute. Watt judged that the horse could pull with a

Watt defined and calculated the horsepower as 32,572 ft⋅lbf/min, which was rounded to an even 33,000 ft⋅lbf/min.^{[7]}

Watt determined that a pony could lift an average 220 lbf (0.98 kN) 100 ft (30 m) per minute over a four-hour working shift.^{[8]} Watt then judged a horse was 50% more powerful than a pony and thus arrived at the 33,000 ft⋅lbf/min figure.^{[9]}^{[better source needed]} *Engineering in History* recounts that ^{[10]} ^{[11]} James Watt and Matthew Boulton standardized that figure at 33,000 foot-pounds (44,742 N⋅m) per minute the next year.^{[11]}

A common legend states that the unit was created when one of Watt's first customers, a brewer, specifically demanded an engine that would match a horse, and chose the strongest horse he had and driving it to the limit. Watt, while aware of the trick, accepted the challenge and built a machine which was actually even stronger than the figure achieved by the brewer, and it was the output of that machine which became the horsepower.^{[12]}

In 1993, R. D. Stevenson and R. J. Wassersug published correspondence in *Nature* summarizing measurements and calculations of peak and sustained work rates of a horse.^{[13]} Citing measurements made at the 1926 Iowa State Fair, they reported that the peak power over a few seconds has been measured to be as high as 14.9 hp (11.1 kW)^{[14]} and also observed that for sustained activity, a work rate of about 1 hp (0.75 kW) per horse is consistent with agricultural advice from both the 19th and 20th centuries and also consistent with a work rate of about 4 times the ^{[13]}

When considering ^{[15]}
and 0.35 hp (0.26 kW) for a period of several hours.^{[16]} The Jamaican sprinter ^{[17]}

Other Languages

العربية: حصان (وحدة قدرة)

azərbaycanca: At gücü

Bân-lâm-gú: Bé-la̍t

беларуская: Конская сіла

беларуская (тарашкевіца): Конская сіла

български: Конска сила

català: Cavall de vapor

čeština: Koňská síla

dansk: Hestekraft

Deutsch: Pferdestärke

eesti: Hobujõud

Ελληνικά: Ίππος (μονάδα ισχύος)

español: Caballo de vapor

Esperanto: Ĉevalpovo

euskara: Zaldi-potentzia

فارسی: اسب بخار

français: Cheval-vapeur

Frysk: Hynstekrêft

Gaeilge: Each-chumhacht

galego: Cabalo de vapor

한국어: 마력

հայերեն: Ձիաուժ

हिन्दी: अश्व शक्ति

hrvatski: Konjska snaga

Bahasa Indonesia: Daya kuda

íslenska: Hestafl

italiano: Cavallo vapore

עברית: כוח סוס

ಕನ್ನಡ: ಅಶ್ವ ಸಾಮರ್ಥ್ಯ

қазақша: Ат күші

kurdî: Hespxurtanî

latviešu: Zirgspēks

lietuvių: Arklio galia

magyar: Lóerő

മലയാളം: കുതിരശക്തി

Bahasa Melayu: Kuasa kuda

монгол: Морины хүч

မြန်မာဘာသာ: မြင်းကောင်ရေအား

Nederlands: Paardenkracht

日本語: 馬力

Nordfriisk: PS

norsk: Hestekraft

norsk nynorsk: Hestekraft

oʻzbekcha/ўзбекча: Ot kuchi

polski: Koń mechaniczny

português: Cavalo-vapor

română: Cal putere

русский: Лошадиная сила

Scots: Horsepouer

Simple English: Horsepower

slovenčina: Kôň (jednotka)

slovenščina: Konjska moč

српски / srpski: Коњска снага

srpskohrvatski / српскохрватски: Konjska snaga

suomi: Hevosvoima

svenska: Hästkraft

தமிழ்: குதிரைத் திறன்

తెలుగు: అశ్వ సామర్థ్యం

ไทย: แรงม้า

Türkçe: Beygir gücü

Türkmençe: At güýji

українська: Кінська сила

اردو: اسپی طاقت

Tiếng Việt: Mã lực

Yorùbá: Horsepower

粵語: 馬力

中文: 馬力