Enter the mass of the object being lifted and the number of ropes between pulley sets into the calculator to determine the effort force or weight of the pulley.

Pulley Weight Formula

The following formula is used to calculate the weight or effort force of a pulley system. 

eF = (m*g) / (u*n)
  • Where eF is the effort force
  • m is the mass of the object
  • g is the acceleration due to gravity
  • u is the friction factor of the system (=1 for ideal systems
  • n is the number of ropes between the pulley sets of pulleys

To calculate the pulley weight effort, multiply the mass by the acceleration from gravity, then divide by the product of the friction factor times the number of ropes between pulley sets.

Pulley Weight Definition

Pulley weight is defined as the weight or effort force seen by the end of a pulley system when lifting an object of set mass at a constant speed.

Pulley Weight Example

How to calculate a pulley weight?

First, determine the mass of the object being lifted. For this example, the object being lifted is 20 kg.

Next, determine the friction factor for the system. In short, this is the mechanical efficiency of the system. For a system with no friction at all this would be equal to 1. For this problem, we will assume the factor is .8.

Next, determine the number of ropes in between the pulleys. This is the number of ropes not including the end ropes being pulled and directly attached to the object.

For this problem, we are looking at a pulley system of 4 pulleys with 4 ropes in between.

Finally, calculate the pulley weight/effort force using the formula.

eF = (20*9.81)/(.8*4) = 61.3125 N