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Torque Calculator and Torque – Power Relationship

In this engineering calculation content, we will show you how to calculate torque quickly. With this torque calculation, you will be able to quickly calculate the torques of physical systems. In the publication of all these, we will explain the torque-power relationship you need to know.

What is Torque Calculation Required For?

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When starting any project, one of the most important features that the user should know about a physical system is torque. If the motor torque information is not available, the torque must be measured or calculated.

If you know the power and speed of the engine you have, you can calculate the torque of your engine by using the torque calculation section below. In this article, the unit of power you should use is Watt, and the number of revolutions is the number of revolutions your engine completes in one minute(rpm).


Pi is considered to be 3.141592653589793

What Is Torque?

Torque is the thrust or torque transmitted from the engine to the moving parts (wheel, gear, track…etc). In an assembly with a wheel attached to the shaft of a motor, as shown in the figure below, torque is equal to force multiplied by the length of the motor shaft. (T = F x d). The unit of torque in Newton-meters (Nm).

The power of a motor is equal to its torque multiplied by its angular velocity. ( P = T x w ) Motor power (P) is equal to the product of the voltage applied to the motor and the current drawn by the motor. ( P = V x I ) The angular velocity is twice the frequency of the motor (the number of revolutions the motor completes in one second) multiplied by the pi number. ( w = 2 x pi x f )

Work done;

The work done is the force multiplied by the distance the force has traveled, and,

W = Fs (1)

W = work done (J, Nm)

F = Force (N)

s = distance moved by the force (s)

For angular motion,

The work done can be expressed as

W = F θ r

= T θ (2)

W = Work (Joules)

θ = Angle (radians)

r = Radius (m)

T = Torque or moment (Nm)

transmitted power

Power is the ratio between the work done and the time taken and can be expressed as,

P = W / dt

= T θ / dt

= T ω

= 2πnT

= 2 π (nrpm / 60) T

= 0.105 nrpm T (3)

P = Power (Watts)

dt = Elapsed time (s)

ω = θ / dt = 2 π n = Angular velocity (rad/s)

n = Speed (Revolutions/s)

nrpm = Speed (Revolutions/min, rpm)

Note! – a machine must rotate to generate power! A machine without rotational motion can provide torque like an electric motor – but because distance does not move forcibly – no power is produced. As soon as the machine starts to spin, power is generated.

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Example – Torque required for power generation

A machine spins at 3000 rpm (rpm) and uses 5 kW. The torque on the shaft can be calculated by replacing (3).

T = P / 2 π n

= (5 kW) (1000 W/kW) / 2 π (3000 rev/min) / (60 sec/min)

= 15.9 Nm


The torque calculation is very simple like above. Do not forget to leave your comments and questions below about the torque calculations in engineering and physics!
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