Horsepower to Foot-pounds Per Second (hp to ft⋅lbf/s)
1 horsepower equals 550 foot-pounds per second exactly.
How to convert horsepower to foot-pounds per second
To convert horsepower to foot-pounds per second, multiply the number of horsepower by 550. This factor is exact. To go the other way, multiply foot-pounds per second by 0.001818181818 (rounded).
foot-pounds per second = horsepower × 550
Example: 10 horsepower = 5,500 foot-pounds per second.
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
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
Foot-pound Per Second (ft⋅lbf/s)
About 1.3558 watts. A horsepower is 550 of these.
Engineers in the English-speaking world measured work as force times distance, so a pound-force lifted through a foot became a foot-pound, and doing it each second gave the foot-pound per second. It is the base from which horsepower is built, since the imperial horsepower is defined as 550 foot-pounds per second, or 33,000 per minute, the figure fixed by James Watt and Matthew Boulton in 1783.
In SI terms one foot-pound per second is about 1.3558 watts, and NIST lists 1.355818 watts without marking it exact. The reverse is 1 watt equal to 0.7375621 foot-pounds per second. Multiplying 550 by 1.3558 gives about 745.7 watts, the usual value for a mechanical horsepower. The unit is rarely quoted on its own today, though it appears in older mechanics texts and in small-scale power estimates.
1 foot-pound per second = 1.355817948 watts (approximately).
Sources: Wikipedia: Horsepower; Wikipedia: Watt; NIST SP 811, Appendix B.8
Related conversions
- Foot-pounds per second to horsepower (reverse)
- Horsepower to watts
- Horsepower to kilowatts
- Horsepower to megawatts
- Horsepower to gigawatts
- Horsepower to metric horsepower
- Horsepower to BTU per hour
- Horsepower to milliwatts
- Horsepower to electrical horsepower
- Horsepower to tons of refrigeration
- Horsepower to kilocalories per hour
- Horsepower to calories per second
- Horsepower to ergs per second
- Watts to foot-pounds per second
- Kilowatts to foot-pounds per second
See all power units.