Choose how many rope parts hold the load, the pulley type and where you pull from. Get the real pull force with pulley friction, how much rope you pull, and the load on the anchor.
Rope parts holding the load
You pull from
Extra stage (compound)
A second tackle pulling on the lead of the first multiplies the advantage, like a Z-drag in rope rescue.
Pulley type
η per sheave
kg
m
kN
From the rope label or datasheet (breaking load ÷ safety factor). Optional.
Pull the rope, the load rises
Compare rigs
Pull force for this load with the selected pulleys. Friction means each extra sheave adds less than the one before.
Parts
Ideal advantage
Real advantage
Pull force
Rope to pull
Friction loss
How it is calculated
n is the number of rope parts holding the moving block, η the efficiency of one sheave (the share of tension that gets past it), W the load. Rope tension drops by η each time it passes a sheave.
Ideal advantage MA = n
Pull from top block W = P · (η + η² + … + ηⁿ) the lead passes one more sheave
Pull from moving W = P · (1 + η + … + ηⁿ⁻¹)
Real advantage MA_real = W / P
Rope pulled s = n · h (compound: n₁ · n₂ · h)
Anchor (top block) F = W + P (pulling down), W − P (pulling up from the moving block)
Compound MA = MA₁ · MA₂
Typical sheave efficiency: plain bushing 0.90–0.92, ball or roller bearing 0.95–0.98, rope over a carabiner or bar about 0.5. Lift loads only with certified hoists and rigging; this tool is for planning and teaching.