How this selector works

Both modes follow the same three steps: compute the rope tension, multiply by a safety factor to get the required minimum breaking force, then find the smallest standard rope whose ISO 2408 breaking force exceeds it.

Lifting slings mode

The force in each sling leg grows with the sling angle — the same load pulls harder on angled legs:

S = W · g / (n_eff · cos β)

W = load (t) · n_eff = effective legs (3- and 4-leg slings count as 2 unless equalized) · β = angle to vertical. At 45°, each leg carries 1.41× its vertical share.

Towing & transport mode

S = W · g · (μ · cos θ + sin θ)

μ = friction coefficient (sliding ≈ 0.15–0.20, rolling ≈ 0.05–0.10) · θ = slope angle. On a slope, gravity adds a component along the pull direction.

From tension to rope diameter

F_{min required} = S × Z_p

F_min(kN) = K × d² × R_r / 1000 → d = √(1000 · F_min / (K · R_r))

ISO 2408 minimum breaking force. K = 0.356 (IWRC steel core) or 0.330 (fiber core) for 6×36 class · R_r = rope grade (N/mm²) · d in mm, rounded up to the next standard diameter.

The shackle suggestion (lifting mode) picks the smallest standard bow shackle whose working load limit covers the leg force.

Application / mechanism class	Minimum Z_p	Notes
M1–M3 hoisting mechanisms	3.55 – 4.0	Light, infrequent duty
M4 mechanisms	4.0
M5 mechanisms	4.5
M6 mechanisms	5.6	Heavy duty hoists
M7 mechanisms	7.1
M8 mechanisms	9.0	Severe continuous duty
Wire rope slings (lifting)	≥ 6.0	Typical statutory minimum
Towing / equipment transport	4 – 6	5.0 common practice

Z_p values per ISO 4308-1 for running ropes; sling minimums per common national lifting regulations. Always follow the standard governing your site.

Rope Ø (mm)	F_min — 1770 IWRC (kN)	F_min — 1770 FC (kN)	≈ Max sling leg load @ Z_p=6 (t)

Computed from ISO 2408: F_min = K·d²·R_r/1000 with K = 0.356 (IWRC) / 0.330 (FC). Manufacturer catalog values may differ slightly — always verify against the rope certificate.

Based on ISO 2408 breaking force formula and ISO 4308-1 safety factor classes. This tool gives a design-stage reference; final rope selection must be verified against the rope manufacturer's certificate and the regulations governing your site. © Kinocranes.

Force per sling leg	56.6 kN
Required min breaking force	339.8 kN
Selected rope breaking force	362.9 kN
Strength margin	+6.8%
Matching bow shackle	WLL 6.5 t (7/8")

Wire Rope Selector

Load & sling arrangement

Rope specification

Equipment & transport conditions

Rope specification

How this selector works

Lifting slings mode

Towing & transport mode

From tension to rope diameter

Wire Rope Selector

Load & sling arrangement

Rope specification

Equipment & transport conditions

Rope specification

How this selector works

Lifting slings mode

Towing & transport mode

From tension to rope diameter

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