Wire Rope Size Chart

ASME B30.9 recommends a minimum 5:1 safety factor for wire rope in lifting service. Some specialized equipment uses 3.5:1, and critical lifts may require 10:1.

Breaking load (minimum breaking strength) is the load at which the rope fails. WLL = breaking load ÷ safety factor. For a 20mm 6×19 IWRC rope with a 25.5 t breaking load at 5:1, WLL = 5.1 tonnes.

6×19 has 19 wires per strand — stiffer, more abrasion-resistant, good for general rigging. 6×36 has 36 wires per strand — more flexible, better fatigue life over sheaves, ideal for crane hoist ropes.

6×7 is the stiffest common construction. Use it for static lines, guy ropes, and stays where the rope won't bend over sheaves. Never use 6×7 in high-cycle bending applications.

IWRC stands for Independent Wire Rope Core. It is a small wire rope at the center of the main rope, replacing the fibre core (FC). IWRC provides approximately 7.5% higher breaking load, better crush resistance under load, and longer service life in dynamic lifting applications.

EIPS (Extra Improved Plow Steel) refers to wire tensile strength of 1960 N/mm² — the standard grade for most lifting rope in ISO 2408 tables. EEIPS (Extra Extra Improved Plow Steel, 2160 N/mm²) gives slightly higher breaking loads at the same diameter, used where weight savings matter.

ASME B30.9 requires removing wire rope if any of these are found: 10 or more broken wires in one rope lay length; 5 or more broken wires in one strand per lay; a visible kink, bird-cage, or crush; diameter reduction greater than 1/3 of original; corrosion pitting; or heat damage and excessive wear.

A 16mm 6×19 IWRC EIPS (1960 N/mm²) wire rope has a minimum breaking load of approximately 14.7 tonnes per ISO 2408. At a 5:1 safety factor, WLL = 14.7 ÷ 5 = 2.94 tonnes. Use the Wire Rope Capacity Calculator above for any diameter and construction.