The working load of a wire rope depends on the intended use for the wire rope.
For lifting slings, the safety factor is 5 to 1. So, to calculate, the minimum break load is divided by 5, then allowances for the type of end termination or the way it is being used must also be considered (I.E.: if choked a reduction of 20% is applied).
Ropes used in other applications may have differing safety factors applied. Those used in staying applications or the forestry sector work on a 3 to 1 safety factor. For ropes used on cranes, the safety factor depends on the classification of the cranes, which can be found in ISO 16625.