Tree Work
Rigging Point Load Calculator
When you redirect a load through a rigging point, the angle between the two rope legs changes the force on the anchor. A 1,000 lb load on legs at 120° puts 2,000 lb on the anchor. Enter the load and angle to see the math.
Force on anchor (lb)
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- Force per leg (lb)
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- Anchor multiplier
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- Sling angle factor (from horizontal)
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FAQ
Why does the angle matter so much? +
As the angle between legs opens up, leg tension increases dramatically. At 120° each leg carries the full load weight; at 150° each leg carries about twice the load. Keep sling angles tight (<60°) when possible.
What is the "anchor multiplier"? +
It is the total force on the anchor point divided by the load weight. At 60° between legs the multiplier is 1.0 — the anchor sees what the load weighs. At 120° it is 2.0. At 170° it is over 11.
Where do most failures happen? +
Rigging point anchor failures often come from operators not realizing how much the angle is opening up as the load shifts during a cut. Always pre-calc worst-case angle, not just rest position.