Pulley System Calculator
A pulley system reduces the force needed to lift a load by distributing it across multiple rope segments. The mechanical advantage equals the number of supporting ropes: with 4 supporting ropes, you need only one-quarter of the load's weight as effort. This calculator determines the ideal and actual effort force (accounting for friction) and the velocity ratio.
In an ideal pulley system, the mechanical advantage (MA) equals the number of rope segments supporting the load. A single fixed pulley (MA = 1) only changes the direction of force. A single movable pulley (MA = 2) halves the required effort. Compound systems with multiple pulleys can achieve any integer MA.
The trade-off is distance: with MA = 4, you pull 4 meters of rope for every 1 meter the load rises. This is the velocity ratio, which equals the MA in an ideal system. Work input always equals work output in a frictionless system (force × distance = constant), consistent with conservation of energy.
Real pulley systems lose efficiency to friction in the pulleys and rope stiffness. Each pulley typically adds 2–10% friction loss. The actual effort force is higher than ideal: effort = load / (MA × (1 - friction%)). Block-and-tackle systems, cranes, elevators, and sailboat rigging all rely on pulley mechanics to multiply human or motor effort.