BravoCalc

Horsepower Calculator

Horsepower Calculator
Calculate horsepower from torque and RPM, or convert between power units

What is Horsepower?

Horsepower (hp) is a unit of measurement for power, which is the rate at which work is done. It was originally created by engineer James Watt in the late 18th century to compare the output of steam engines with the power of draft horses. One mechanical horsepower is equal to 745.7 watts or 550 foot-pounds per second.

How to Calculate Horsepower

There are several ways to calculate horsepower, depending on the application:

1. From Torque and RPM

The most common formula for calculating horsepower in engines is:

HP = (Torque × RPM) ÷ 5,252

Where:

  • HP = Horsepower
  • Torque = Rotational force in pound-feet (lb-ft)
  • RPM = Revolutions per minute
  • 5,252 = A constant derived from the conversion between torque and horsepower

2. From Force and Speed

For linear motion, horsepower can be calculated as:

HP = (Force × Distance) ÷ (Time × 550)

Where:

  • Force = Force in pounds
  • Distance = Distance in feet
  • Time = Time in seconds
  • 550 = The number of foot-pounds per second in one horsepower

Types of Horsepower

  • Mechanical/Imperial Horsepower: The standard unit equal to 745.7 watts.
  • Metric Horsepower (PS or CV): Slightly smaller than mechanical horsepower, equal to 735.5 watts.
  • Electrical Horsepower: Equal to exactly 746 watts.
  • Boiler Horsepower: A unit used for rating steam boilers, equal to 9,809.5 watts.
  • Brake Horsepower (BHP): The measure of an engine's power without the loss in power caused by the gearbox, generator, differential, water pump, and other auxiliary components.

Horsepower vs. Torque

While horsepower measures the rate at which work is done, torque measures the rotational force that causes the work. In simple terms:

  • Torque: The twisting force that causes rotation. It's what you feel when you accelerate.
  • Horsepower: How quickly that twisting force can be delivered. It's what you feel at higher speeds.

In vehicles, high torque is beneficial for towing, climbing hills, and accelerating from a stop, while high horsepower is beneficial for maintaining high speeds and accelerating at higher speeds.

Power Unit Conversions

  • 1 Horsepower (hp) = 745.7 Watts (W)
  • 1 Horsepower (hp) = 0.7457 Kilowatts (kW)
  • 1 Kilowatt (kW) = 1.341 Horsepower (hp)
  • 1 Metric Horsepower (PS) = 0.9863 Mechanical Horsepower (hp)
  • 1 Mechanical Horsepower (hp) = 1.0139 Metric Horsepower (PS)
  • 1 Horsepower (hp) = 550 foot-pounds per second
  • 1 Horsepower (hp) = 33,000 foot-pounds per minute