What is horsepower

Horsepower (HP) is a unit for measuring power or the rate at which work is done. Otherwise, it is a reference to how much energy comes out of the engine.

We have various horsepower standards. The two most commonly used are mechanical horsepower (imperial horsepower), approximately 745.7 watts, and the metric horsepower, 735.5 watts. This term was adopted in the late 18th century by Scottish engineer James Watt to compare the output of steam engines with the power of draft horses. Eventually, this began to be applied with other machinery such as turbines, electric motors.

In short, horsepower is compared to the power produced by the engine. It measures how much energy we need to lift 227 kilograms (550 lbs) to a height of 0.30 meters (one foot) in a time of one second or the power with which it will move 14.968kg (33.000lbs) 0.30 meters (one foot) in time of one minute.

How to calculate horsepower

We use a simple formula to calculate horsepower. Multiply the torque value by the speed values of the engine. You will be using the formula:

Horsepower = (RPM x T) / 5252 = HP

RPM is the engine speed

T is the torque

5,252 is radians per second.


(6.000RPM * 360 LB.FT) / 5,252 = 411HP

Horsepower to watts conversion

One mechanical or hydraulic horsepower is equal to 745.67 Watts

1hp = 745.67 W

Formula for converting horsepower to watts:

P (W) = 745.67 W * P (hp)


Convert 25 hp to watts

P (W) = 745.67 * 25 = 18641.75 W

We can turn this into kilowatts that are more familiar to us in cars.

18641.75 W = 18.64 kW

Horsepower to watts conversion

Before we show you how to turn horsepower into a watt, let’s briefly say what a watt is. Watt is a unit of power in the International System of Units (SI), defined as a unit derivative of 1kg*m^2*s^ -3[\latex] which is equivalent to 1 joule per second. It is used to quantify the rate of energy transfer. It was named after the 18th-century Scottish scientist James Watt.

Watt is the SI-derived unit for power in the metric system. Watts can be abbreviated as W; for example, 1 watt can be written as 1 W.

Watt's Law states the relationship between power, current, and voltage. Using Watt's Law, it's possible to express the power in watts using current and voltage.

One mechanical or hydraulic horsepower is equal to 745.67 Watts

1hp = 745.67 W

Once we know the value of one horsepower, you can convert horsepower to watts using the following formula:

Watts = hp (I) × 745.699872

For example, we will convert the horsepower of the average car to watts (150hp).

Watts = 150 * 745.699872

Watts = 111.854 W or 111.85 kW

Horsepower vs torque

We mention horsepower and torque all the time to explain what it means.

Torque and power are what the engine produces when started. Air and fuel ignite in the combustion chamber and move the crankshaft, transmission, and drive axles to make a turn.

Energy- is the ability of a body to do some work. Energy is found in nature in various forms, converted from one type of energy to another.

Work- is a physical quantity that describes the action of a force.

Torque- is a physical vector quantity that plays a similar role in body rotation as a force in body translation. Torque gives the body angular acceleration.

Power- is a physical quantity that describes the speed of mechanical work, determined by the ratio of work W and the time spent t.

Torque is the capacity of work, while power is how fast some work can be done in a given time. In other words, power is the rate of doing work at a given time. Horsepower is equal to the torque multiplied by rpm. H = T x rpm / 5252, where T is pound-feet, rpm is how fast the engine is spinning, and 5252 is a constant that makes the units jibe.

British Thermal Unit (BTU)

The British Thermal Unit (BTU) is a unit of heat. It is defined as the amount of heat required to raise one pound of water by one degree Fahrenheit at a constant pressure of 1 atmospheric unit. Heat is now known to be equivalent to energy.

One BTU is approximate:

  • 0.2931 Wh (Wat hours)
  • 252-253 calories
  • 0.25 calories
  • 1.054-1-060 kJ (kilojoules)

Different Horsepower’s

We have several types and definitions of horsepower. Below we will list and explain most of them.

Mechanical horsepower: definition of standard gravity, gn = 9.80665 m / s2, is used to define the pound-force as well as the kilogram-force, and the international avoirdupois pound, one mechanical horsepower is: 745.699W

Metric horsepower (PS, cv, HK, pk, ks, ch)

The various units used to indicate this definition (PS, KM, cv, HK, pk, ks, and ch) translate to horsepower in English. One metric horsepower is the power to raise a mass of 75 kilograms against the Earth's gravitational force over a distance of one meter in one second.

75 kg × 9,80665 m / s2 × 1 m / 1 s = 75 kgf⋅m / s = 1 PS

This is equivalent to 735.49875 W

Electrical horsepower: Nameplates on electrical motors show their power output, not the power input (the power delivered at the shaft, not the energy consumed to drive the motor). In the United States, the power output is stated in horsepower, which for this purpose is defined as precisely 746 W.

Mustang GT horsepower

The most common Ford Mustang GT has a top speed of 163 mpg. It is equipped with its famous 5.0-liter V8 engine that produces 480 horsepower and 420 pounds of torque. The Ford Mustang GT packs a lot of power and has a 060 time of 4.1 seconds.

There are other car related calculators on our site, so be sure to check out our Gas Calculator and Winch Size Calculator as well.

Frequently Asked Questions

How much horsepower does a Dodge Demon have?

The 2018 Carbon Demon is powered by a 6.2-liter V8 engine that produces 808 horsepowers and 717 lb-ft of torque. They achieved this by removing the steel body and replacing it with carbon, which saved a lot of weight on the car.

How much horsepower does a horse have?

In one study it was shown that the maximum sustainable mechanical power per kilogram of muscle is between 100 and 200W. That is for an average heavy horse, 24 horsepower. While the second is essentially the maximum horsepower can be up to 15 horsepower.