Find the effort force, mechanical advantage and rope pulled for a pulley system.
Find the effort force, mechanical advantage and rope pulled for a pulley system.
Effort force (N)
How to use this tool
Mass to be lifted, in kilograms.
Count the rope segments that actually support the moving block, not the total rope length.
Friction in real pulleys costs a few percent per sheave; 90% is a reasonable starting estimate.
How far the load rises; rope pulled is lift height times the number of supporting ropes.
Formula & worked example
Load 100 kg (981 N), 4 supporting ropes, 90% efficiency, 1 m lift: effort = 981 / (4 × 0.9) = 272.5 N, actual mechanical advantage 3.6, rope pulled 4 m.
Limitations — read this before you rely on it
This treats efficiency as a single system figure and ignores rope weight, stretch and individual sheave friction, which vary with load and rope type. For lifting people or safety-critical loads, use rated equipment and a qualified rigger.
Frequently asked questions
Each segment of rope attached to or passing under the moving pulley block; the free end pulled by hand does not count unless it also supports the block.
Friction in each pulley bearing and rope bending losses consume some of the effort.
No — pulleys trade force for distance. You pull more rope with less force; total work stays the same apart from friction losses.
A simple two-pulley system with two supporting ropes, giving an ideal advantage of 2.
A single fixed pulley only changes direction (advantage 1); a single movable pulley gives an advantage of 2.