Pulley Calculator — Mechanical Advantage & Effort Force
Enter the load weight, number of supporting rope segments and per-sheave friction to find the effort force you need to apply, the rope you must haul, and the overall system efficiency.
N
%
m
Force you must pull on the free rope end, accounting for friction
- 1
Mechanical advantage
MA = 4 rope segments = 4 - 2
Ideal effort (frictionless)
500 ÷ 4 = 125 N - 3
System efficiency
(1 − 0.05)^3 = 85.7 %Friction losses compound multiplicatively across each sheave. - 4
Actual effort force
125 ÷ 0.8574 = 145.8
How does this calculator work?
A pulley system multiplies your force by the number of rope segments supporting the load (mechanical advantage). Friction in each sheave reduces efficiency by (1 − f) per stage. Actual effort = Load ÷ (MA × efficiency); you must haul MA times the load travel distance. Enter load, segments and friction to get all values.
Formula
How this is calculated
A block-and-tackle pulley system multiplies your pulling force by routing the rope through one or more movable pulleys. The mechanical advantage (MA) equals the number of rope segments directly supporting the load block — so a 4-segment system lets you lift 500 N with just 125 N of ideal effort. The trade-off is distance: you must pull the rope MA times as far as the load travels.
Friction in real sheave bearings reduces efficiency. This calculator uses the model Efficiency = (1 − f)^(n−1), where f is the fractional loss per sheave and n − 1 is the number of sheaves in the system. Typical values are 3–5% loss per roller-bearing sheave and 6–10% for plain-bore bushings. The actual effort needed is the ideal effort divided by the efficiency, and the ratio of useful work output to rope-work input is the same efficiency figure.
The calculation assumes all rope segments run parallel to the load direction and that the load and rope are in static equilibrium. Dynamic loads (acceleration, jerk) and rope weight are not included. Always apply a safety factor appropriate for your rigging application.
Frequently asked questions
Mechanical advantage is the ratio of the load force to the effort force. In a block-and-tackle it equals the number of rope segments supporting the moving (load) block. MA = 4 means you lift 4 × more weight than the force you apply.
Conservation of energy: you multiply force by the same factor you divide distance. To lift a load 1 m with MA = 4 you must pull 4 m of rope. The work done (force × distance) is the same on both sides, minus friction losses.
Each rope-over-sheave contact dissipates energy as heat. The loss accumulates multiplicatively — a 5% loss per sheave over 3 sheaves gives 0.95³ ≈ 86% efficiency, meaning 14% of the work you put in is wasted on friction.
Also known as
TG we-Calculate Editorial Team. (2026). Pulley Calculator — Mechanical Advantage & Effort Force [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/pulley-calculator
TG we-Calculate Editorial Team. "Pulley Calculator — Mechanical Advantage & Effort Force." TG we-Calculate. 2026. https://we-calculate.com/calculator/pulley-calculator.
TG we-Calculate Editorial Team, "Pulley Calculator — Mechanical Advantage & Effort Force," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/pulley-calculator
@misc{wecalculate_pulley_calculator, title = {Pulley Calculator — Mechanical Advantage & Effort Force}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/pulley-calculator}}, year = {2026}, note = {TG we-Calculate} }
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