Power Conversion Calculator

Common Units of Power

Metric System
1 Watt¹ = 1 Joule per second

English
1 Horsepower² (hp) = 746 Watts = 2545 BTU's³ per hour
1 Horsepower (hp) = 550 Foot-pounds⁴ per second

Work
foot-pound: 1-lb force acting through a distance of 1 ft
erg: a 1-dyne⁵ force through 1 cm
joule: 1-newton⁶ force through 1 m

1 foot-pound = 1.356 joules
1 erg = 10^-7 joules

¹ The SI (Systme International) unit of electrical work is the watt. It represents the generation or use of electrical energy at the rate of 1 joule per second. The kilowatt is equal to 1000 watts.

² One horsepower was originally defined as the amount of power required to lift 33,000 pounds 1 foot in 1 minute, or 550 foot-pounds per second.

³ One British Thermal Unit (Btu or BTU) was originally defined as the quantity of heat required to raise the temperature of 1 lb (0.45 kg) of water from 59.5 F (15.3 C) to 60.5 F (15.8 C) at constant pressure of 1 atmosphere. For accuracy, the BTU has now been defined in terms of the joule. One BTU is equal to 1055 joules. A BTU is equivalent to approximately 0.293 watt-hour.

⁴ In English system of units, the unit of work is the foot-pound (ft-lb), which is equal to the amount of work required to raise a mass of 1 lb through an elevation of 1 ft at sea level and 45 latitude.

⁵ A dyne is a centimeter-gram-second unit of force, equal to the force required to impart an acceleration of one centimeter per second per second to a mass of one gram.

⁶ A newton is a meter-kilogram-second system, the unit of force required to accelerate a mass of one kilogram one meter per second per second, equal to 100,000 dynes.