Torque to hp Calculator

Created by Avram Aruh
Reviewed by Hanna Pamuła, PhD candidate and Jack Bowater
Last updated: Jun 02, 2021

This torque to hp calculator helps you find the horsepower of a moving object. There are only a few differences that separate torque vs. hp, so converting hp to torque isn't too difficult. In the text below, you can also find how to convert horsepower to torque (nm) and the horsepower formula explained in detail. You can also use this tool to convert gross torque to horsepower if you know the torque of your engine!

What is horsepower? Horsepower definition

Imagine a horse attached to a wheel; the wheel starts at rest, but as soon as the horse starts pulling, it moves. The horse will move this wheel a certain distance over a second, which is known as a horsepower - the rate of work that is done. Horsepower is generally used to identify an engine's or motors' efficiency and was first defined in the late 18th century by Scottish engineer James Watt, when he wished to compare an engine's efficiency with a horse.

When people are talk about horsepower, they generally mean mechanical horsepower. However, there are many different types of horsepower, such as;

  • Mechanical Horsepower, hp(I): The most common horsepower definition, mechanical horsepower is equal to 745.70 Watts.

  • Metric Horsepower, hp(M): A more scientific designation, approximately 735.50 Watts.

  • Electrical Horsepower, hp(E): This equals 746 Watts. This definition is mainly used for electrical motors.

  • Air Horsepower, ahp: This equals 944 Watts, and is used mainly in air conditioning machines.

  • Boiler Horsepower, hp(S): This denotes a boiler's capacity to deliver steam to a steam engine, which equals approximately 9,809.5 Watts.

💡 When we want to convert gross torque to horsepower,we have to know how many watts are in one horsepower for that particular type of device (e.g., in an electric motor, 1 horsepower equals 746 Watts).

What is torque? Torque definition

Torque is the ability of a force to turn or twist an object. Torque is present if, when we apply a force to an object, it begins to spin or stops spinning. Torque depends on the radius of the object (in meters) multiplied by the force being applied to it (in Newtons). Therefore, the SI unit of torque is N.m.

Speed answers the question "How fast is an object moving?" Speed is the distance an object covers in a period of time, and doesn't depend on the direction the object is travelling (known as a scalar unit). Speed can either be linear (m/s, mph) or circular (rpm, rad/s).

Torque vs. hp

When we talk about vehicles, we often hear the words horsepower and torque, but do we actually know what these units represent? There are a few differences between torque vs. hp:

Let's remember that torque is a force that acts on an object to rotate it. On the other hand, horsepower is how far that object moves over a certain time when a force is applied to it. And so, horsepower is the torque applied to an object multiplied by the speed this amount of torque produces over a certain period of time:

Horsepower = Torque x Speed

When we want to compare things like acceleration and top speed, we should be looking at horsepower. Imagine a vehicle on a slope, and we want to know "It is possible for this vehicle to climb this hill easily?" If the vehicle has sufficient torque, it will have no problems getting to the top of the hill.

How do we calculate horsepower? Hp to torque formula

As we covered the definitions of torque, speed, and horsepower, the formula of horsepower can be thought of as the torque applied to an object and the speed this force produces over a given period of time. In this section, we will show you how the torque to hp calculator works with an example:

  1. When we want to convert gross torque to horsepower, we need know the formula of power in Watts:

Power (W) = Torque (N.m) * Speed (rpm)

  1. Let's calculate the mechanical horsepower of a machine with a 150 N.m torque value and 1500 rpm speed:

Power (W) = 150 N.m * 1500 rpm = 225,000 Watts

  1. As we calculated the power of our machine in Watts, we can calculate mechanical horsepower by applying the appropriate horsepower conversion:
💡 We know that 1 mechanical hp equals 745.70 W

Horsepower (hp(I)) = Power (W)/745.70 W

  1. So, the mechanical horsepower (hp(I)) of this machine can be calculated by the following calculation:

Horsepower (hp(I)) = 225,000/745.70 W = 31.6 hp(I)

  1. And that's it. Now we know that this device produces 31.6 hp. Now you're ready to use the torque to hp calculator!
Avram Aruh
Horse power
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