Enter the total axial force, the radius of the drive pulley, and the efficiency of the system into the calculator to determine the pulley torque.

Pulley Torque Formula

The following formula is used to calculate the torque acting on a pulley in a belt-drive system.

T = F*r / n

  • Where T is the torque (N*m)
  • F is the force (N)
  • r is the radius of the drive pulley (m)
  • n is the efficiency of the system

Pulley Torque Definition

A pulley torque is defined as the total torque acting on a drive pulley of a belt-drive system moving at a constant velocity.

Example Problem

How to calculate pulley torque?

To calculate a pulley torque, first determine the force acting on the pulley. This is usually calculated using the motor force acting on the pulley. For this problem, the force is calculated to be 200 N.

Next, determine the radius of the drive pulley. In this problem, the drive pulley is measured to be .35 m.

Next, determine the efficiency of the system. This is the approximate efficiency rating of the belt-drive system after taking into account friction and losses in the transferring of force from the motor to the pulley or vise versa. We will use a conservative .75 for this problem.

Finally, calculate the pulley torque using the formula:

T = F*r / n

= 200 * .35 / .75

= 93.333 N*m.


Do pulleys multiply torque?

Yes, pulleys can and do multiply torque. This happens because while the force delivered to the pulleys is the same, the size of the radius of the pulley is different therefore changing the torque since torque is equal to force times distance.

While the pulley will increase torque, it is at the expense of speed, since the power delivered will be the same.

What is the torque on a pulley?

The torque on a pulley is calculated by multiplying the force on the belt by the radius of the drive pulley.

pulley torque calculator