By Zencalcy Editorial TeamLast reviewed About us
In a block-and-tackle, the load is shared among the rope segments that support the moving block. With n supporting segments the effort is the load divided by n, at the cost of pulling n times as much rope.
Effort and load for a block-and-tackle with n supporting ropes.
F_effort = F_load / n
n is the number of rope segments supporting the moving block. A single fixed pulley has n = 1; a movable pulley with two supporting segments has n = 2.
| Symbol | Meaning |
|---|---|
| F_effort | Force applied to the rope, in newtons. |
| F_load | Load being lifted, in newtons. |
| n | Number of supporting rope segments. |
The effort is 500 / 4 = 125 N. You pull 4 m of rope for every 1 m the load rises, keeping work unchanged in an ideal system.
Continue with the Screw Mechanical Advantage Calculator, Wedge Mechanical Advantage Calculator, or the Wheel and Axle Calculator — or browse more simple machines tools and all physics calculators.
Count the segments that pull upward on the moving block. A rope segment that only passes over a fixed pulley above does not support the load.
Results are computed from the standard equations of classical mechanics. Unit conversions use the SI definitions published by NIST. Air resistance is ignored unless the calculator names a drag model.
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Content updated: September 2026