Rigging Load Calculator

Each leg's load is design load divided by (number of legs times the cosine of half the bridle angle), not simply design load divided by number of legs. As you splay the legs wider, the cosine term shrinks, so the tension per leg actually increases relative to a straight-down single point — wide bridle angles mean each leg is fighting a more direct pull-apart geometry, which is why the calculator caps the trig factor near 90° rather than letting it spike unrealistically at very wide splays.

Design load is the static load (dead plus live load, converted to force via gravity) multiplied by your dynamic factor — it represents the actual force the rigging must handle during use, including shock from drops or catches. Minimum breaking strength is design load multiplied again by your safety factor, representing the rated capacity the hardware itself needs to have well beyond what it will actually experience, which is the number you'd match against manufacturer WLL/MBS specs.

The calculator lets you enter any safety factor of 1 or above with no enforced minimum, but industry practice for life-safety aerial rigging calls for 8:1 to 10:1, versus roughly 5:1 for static scenery that isn't bearing a performer. Entering a lower number than your rigging's actual use case calls for will understate the required breaking strength and should be treated with real caution — the calculator itself does not stop you from doing this.

It's a rough approximation using a common rule for 6x19 IWRC wire rope, where minimum breaking strength in kN is roughly 50 times diameter squared in millimeters, solved backward from your per-leg MBS requirement. It's meant as a starting point for sourcing hardware, not a substitute for a qualified rigger or engineer confirming the actual rope, shackles, and hardware for anything bearing human weight.