How to use the sling angle tension calculator
Hanging a 2,000 lb load from two legs looks like 1,000 lb per leg, but once the legs spread apart each one carries more. This calculator applies T = W / (effective legs × sinθ) to get the real tension in each leg plus the horizontal component. At a 60 degree horizontal angle, a two-leg lift of 2,000 lb puts about 1,155 lb in each leg.
| Horizontal angle θ | Tension factor (1/sinθ) |
|---|---|
| 90° (vertical) | 1.000 |
| 60° | 1.155 |
| 45° | 1.414 |
| 30° | 2.000 |
As the angle flattens, the horizontal component grows even faster than the tension. That horizontal force squeezes the load inward, which can buckle thin plate or crush box-shaped items. Below a 30 degree horizontal angle the tension more than doubles, which is why shallower angles are generally prohibited.
A four-leg bridle is computed on three effective legs because a rigid load will not share evenly across all four. Compare the resulting tension against the rated capacity of the sling, shackles and hooks, and confirm the sling tag and crane load chart with a qualified rigger before the lift.
Frequently asked questions
The horizontal angle is measured between the top of the load and the sling leg. The included angle is the angle between the two legs. For a symmetric two-leg lift, included angle = 180 degrees minus twice the horizontal angle, so a 60 degree horizontal angle gives a 60 degree included angle.
In theory yes, in practice no. On a rigid load, leg length tolerance and tilt keep four legs from sharing equally, so standard rigging practice counts only three legs as effective and this calculator does the same.
Use longer slings, or add a spreader or lifting beam so the legs stand closer to vertical. If limited hook height is what forces the shallow angle, the lift plan itself needs to be reworked rather than accepting the extra tension.