Horsepower Calculator

Horsepower quantifies the amount of power—essentially how quickly work is performed. With this tool you can calculate horsepower based on its formal definition and translate it across various power units. If you need to determine a vehicle’s engine horsepower, try our Engine Horsepower Calculator.

Horsepower Calculation Based on Definition

By definition   Power = force×

distance time

Force:	newton kilonewton pound-force kilogram-force
Distance:	meter kilometer mile yard
Time:	second minute hour day

Horsepower Converter

Converts between different units of power.

Amount:	Convert From:	Convert To:
	Watt Kilowatt Mechanical Horsepower Metric Horsepower Electrical Horsepower Boiler Horsepower BTU/h	Watt Kilowatt Mechanical Horsepower Metric Horsepower Electrical Horsepower Boiler Horsepower BTU/h

Horsepower

The unit of horsepower was devised by engineer James Watt in the late 18^th century. Originally intended to relate the output of steam engines to the pulling power of a horse—hence the name—it has since become a generic measure for countless engines, from automobiles and lawn mowers to boats, chainsaws and aircraft.

Today, horsepower is commonly invoked to describe the theoretical work a vehicle’s engine can deliver, making it a popular benchmark for performance. While it offers a useful snapshot, it isn’t the sole factor in assessing a car’s capabilities; aspects like power‑to‑weight ratio, torque, drivetrain layout and forced induction also matter. For deeper insight or to run your own calculations, visit the Engine Horsepower Calculator.

When measuring horsepower output of anything, to ensure precise comparisons between them, it is important to be consistent in the methodology used to determine horsepower.

Watt

Horsepower isn’t part of the International System of Units (SI); the SI standard for power is the watt, named after James Watt. One watt equals one joule per second and is handy for low‑power applications such as lighting or charging a phone. Larger loads are usually expressed in kilowatts—think refrigerators, servers or other high‑consumption devices. Energy consumption is often billed in kilowatt‑hours (kWh) by electric utilities.

BTU

Another energy unit is the British Thermal Unit (BTU), defined as the heat needed to raise one pound of water by one degree Fahrenheit. Interestingly, a single match releases roughly the same amount of energy as one BTU. BTUs are frequently used to compare fuel energy content. One BTU equals about 0.293 watt‑hours or 1,055 joules.

Different Horsepowers

When people mention horsepower they are generally talking about mechanical horsepower, although the term also has several less common definitions.

• Mechanical Horsepower, hp(I) — 550 foot-pounds per second, roughly 745.7 watts. This is the classic definition introduced by James Watt in 1782.
• Metric Horsepower, hp(M)—75 kgf-m per second, approximately 735.499 watts
• Boiler Horsepower, hp(S) — the ability to evaporate 34.5 pounds of water per hour at 212°F, about 9,809.5 watts. It gauges a boiler’s steam‑producing capacity.
• Electrical Horsepower — approximately 746 watts. This standard is applied to electric motors.

	Search