WLL.wtf

A working load limit (WLL) cord calculator for suspension practitioners

Derated Minimum Breaking Strength `fc = Fiber Class %` `fc × mbs = dMBS (derated MBS)` `0.5 × 0 = 0`
0 lbs	(50%)

Working Load Limit `sf = Safety Factor` `dMBS ÷ sf = wll` `0 ÷ 10 = 0` `0 × 2 = 0 Per Basket`
Per Line	0 lbs
Per Basket	0 lbs

Minimum Cord Needed `Load ÷ wll = Minimum Lines` `0 ÷ 0 = 0` `0 ÷ 2 = 0 Minimum Baskets`
Lines	0
Baskets	0

fc × mbs ÷ sf = wll

Minimum Breaking Strength (MBS): the maximum amount of force a material can withstand before it breaks completely under a straight pull. The cord manufacturer should specify the MBS.

Working Load Limit (WLL): the maximum weight as defined by the manufacturer that a user is allowed to apply to a lifting medium in the performer flying system.

Fiber Class (FC): A classification used in cordage standards to group rope fibers by mechanical behavior. Class 1 fibers (nylon, polyester, polypropylene) have moderate stiffness. Class 2 fibers (HMPE/Dyneema, aramid, LCP) are high-modulus fibers. Modulus (elastic modulus) is a measure of stiffness — how much a material resists stretching under load.

Composite Fiber (Hybrid Construction): A cord made with two or more fiber types in its load-bearing structure (for example, a polyester sheath over an HMPE core). In cordage standards, if any load-bearing component contains Class 2 (high-modulus) fiber, the cord is classified and derated as Class 2, since the lowest knot efficiency governs overall strength.

Derating Cord: The MBS of the cord needs to be derated by 50% for Class 1 fibers and 70% for Class 2 fibers to account for knots and terminations, which reduce the strength of the cord.

Characteristic Load: the maximum force applied to the system resulting from normal intended operating conditions while the system is at rest or in motion.

Safety Factor (SF): the ratio between the designated working load limit (WLL) and the load the equipment is expected to fail at. When selecting an appropriate cord for use with body suspension, a safety factor of 10 needs to be employed. This safety factor takes into account dynamic forces and unknown variables but not terminations.

This calculator is designed to assist you in selecting the most appropriate cord for your specific application. Please note: While overall tensile strength is important, other properties should also be considered when choosing cord for critical applications. Use this tool as a guide only.