Stainless Steel Wire Rope Breaking Strength Chart [2026 Reference]

How Wire Rope Breaking Strength Is Measured

Breaking strength — also called minimum breaking force (MBF) or minimum breaking load (MBL) — is the maximum tensile load a wire rope can withstand before it fractures. It is the single most important number on any wire rope specification sheet, because every other load rating derives from it.

Testing is performed on a full-diameter sample of finished rope, not on individual wires. The rope is gripped in standardized capstan or resin-socket terminations and pulled in a tensile testing machine at a controlled rate until failure occurs. The peak load recorded at fracture is the actual breaking strength of that specimen. For a full overview of tensile, NDT, and proof-load techniques, see our wire rope testing methods and standards guide.

Key Standards

Several international standards govern how stainless steel wire rope is manufactured, tested, and rated:

• GB/T 9944-2015 — the primary Chinese national standard for stainless steel wire rope. It defines constructions, tensile grades (1570 MPa and 1770 MPa), and minimum breaking force values for every combination of construction and diameter.
• ASTM A492 — the U.S. standard specification for stainless steel rope wire. It covers chemical composition and mechanical properties for grades 302, 304, 305, 316, and others used in wire rope production.
• DIN 3055 / EN 12385 — European standards that specify requirements for steel wire ropes including stainless grades. EN 12385 is the current harmonized standard across EU member states.
• ISO 2408 — the international standard for steel wire ropes, specifying general requirements, breaking force tables, and test methods.

All published breaking strength values are minimum guaranteed values. The actual breaking strength of a well-made rope typically exceeds the minimum by 5–15%. At Qianjun, every production lot undergoes destructive break testing on sample lengths to verify compliance with GB/T 9944 and applicable export standards.

How the Minimum Breaking Force Is Calculated

The theoretical breaking force of a wire rope is derived from the aggregate cross-sectional area of all load-bearing wires, the nominal tensile strength grade of the wire, and a spin loss factor (also called the stranding factor or rope factor). When individual wires are twisted into strands and strands are laid into rope, they follow a helical path rather than a straight line. This helical lay reduces the effective contribution of each wire to the rope's axial strength. The spin loss factor accounts for this reduction and typically ranges from 0.80 to 0.97, depending on the construction complexity.

The formula is: MBF = d² × K × R, where d is the nominal rope diameter in mm, K is a construction-specific constant that incorporates the fill factor and spin loss, and R is the wire tensile grade in N/mm². For practical engineering, however, you should always reference the published minimum breaking force tables rather than calculate from first principles.

Breaking Strength by Construction and Diameter

The tables below list the minimum breaking force for the three most commonly specified stainless steel wire rope constructions. Values are given for the 1770 MPa tensile grade, which is the standard grade for most commercial and industrial applications. For 1570 MPa grade, multiply the listed values by approximately 0.887 (i.e., 1570 ÷ 1770). All values comply with GB/T 9944-2015 and are verified through our in-house break testing program.

1x19 Construction — Rigid / High-Strength

The 1x19 construction consists of a single strand of 19 wires. It has the highest strength-to-diameter ratio of any common construction, with a breaking load factor of 0.95. Its low elongation and high rigidity make it ideal for standing rigging, guardrail infill cables, balustrade wire, and architectural tension members where minimal stretch is required.

7x7 Construction — General Purpose

The 7x7 construction has 7 strands of 7 wires each (49 wires total). It provides an excellent balance between flexibility and abrasion resistance, with a breaking load factor of 0.88. This is the most widely used construction for general-purpose applications including control cables, lashing, trellis wire, and light rigging where moderate flexibility is needed.

7x19 Construction — High Flexibility

The 7x19 construction has 7 strands of 19 wires each (133 wires total). It offers the highest flexibility among the three constructions listed here, with a breaking load factor of 0.85. The large number of fine wires allows the rope to bend around small radii without fatigue, making it the preferred choice for running rigging, winch lines, control cables over pulleys, and any application involving repeated bending. For a full breakdown of how these two constructions differ in flexibility and fatigue life, see our 7x7 vs 7x19 wire rope construction comparison.

Note: All values above are for the 1770 MPa tensile grade, which is the standard for stainless steel rope wire per GB/T 9944. For the 1570 MPa grade, reduce the breaking force values by approximately 11.3%. For complete specifications across all constructions including 1x7, 6x7, 6x19, 6x37, 7x37, and 19x7, visit our full specifications page.

Breaking Strength by Diameter

Many engineers and riggers search for wire rope strength by a specific diameter. The sections below provide detailed breaking strength data for each common size, cross-referencing all available constructions. All values are from our GB/T 9944-2015 tables above (1770 MPa grade). Imperial sizes are mapped to the nearest standard metric diameter.

Understanding Safety Factors

The breaking strength of a wire rope is never the load you should apply in service. A safety factor (also called a design factor or factor of safety) is applied to create a margin between the working load and the breaking point. This margin accounts for dynamic loads, shock loads, degradation over time, uncertainty in load estimation, and the consequences of failure.

The safety factor is defined as: Safety Factor = Minimum Breaking Force ÷ Working Load Limit. The required safety factor depends on the application and the level of risk involved:

Safety factor is only one part of the specification process — for a complete walkthrough covering construction, grade, diameter, and coating together, see our how to choose the right wire rope guide.

These safety factors are widely adopted across international codes including ASME B30.9 (slings), EN 13414 (wire rope slings), and AS 1418 (cranes). Some jurisdictions and specific applications may require higher factors — always consult your local regulations and the relevant engineering standard before finalizing your design.

Working Load Limit (WLL) Calculation

The Working Load Limit (WLL), sometimes called Safe Working Load (SWL), is the maximum load that may be applied to a wire rope in normal service. It is calculated by dividing the minimum breaking force by the required safety factor:

WLL = Minimum Breaking Force ÷ Safety Factor

For the complete methodology — safety factor tables for every application, sling angle and D:d bend efficiency derating charts, and an interactive calculator with kgf, lbs, and kN output — see our dedicated wire rope WLL and safety factor calculation guide.

Calculation Example 1 — General Lifting

Suppose you need to select a 7x19 stainless steel wire rope for a winch application with a maximum load of 1,500 lbs. The required safety factor for general lifting is 5:1.

Required minimum breaking force = 1,500 lbs × 5 = 7,500 lbs. Referring to the 7x19 table above, a 5.0 mm diameter rope has a minimum breaking force of 3,912 lbs — too low. A 6.0 mm rope at 5,633 lbs is still not enough. A 7.0 mm rope at 7,665 lbs meets the requirement. Therefore, specify 7x19 construction, 7.0 mm diameter, 1770 MPa grade.

Calculation Example 2 — Personnel Carrying

For a man-riding application with a maximum load of 250 kg (2.45 kN), the safety factor must be at least 7:1. Required minimum breaking force = 2.45 kN × 7 = 17.15 kN. From the 7x7 table, a 5.0 mm rope at 18.86 kN satisfies the requirement. Specify 7x7 construction, 5.0 mm diameter, 1770 MPa grade.

Calculation Example 3 — Static Architectural Cable

An architect specifies 1x19 stainless steel cable for a balustrade infill with a design load of 1.5 kN per cable. For static architectural use, a 3:1 safety factor is typical. Required minimum breaking force = 1.5 kN × 3 = 4.5 kN. From the 1x19 table, a 2.0 mm rope at 4.04 kN is just below the threshold. A 2.5 mm rope at 6.31 kN provides adequate margin. Specify 1x19 construction, 2.5 mm diameter, 1770 MPa grade.

For assistance selecting the right rope diameter and construction for your specific application, see our product catalog or contact our engineering team for a free recommendation.

Factors That Affect Actual Strength

The breaking strength values in the tables above represent the minimum guaranteed performance of a new, straight, properly terminated wire rope tested under controlled laboratory conditions. In real-world service, several factors can reduce the actual strength below the published minimum. Understanding these derating factors is essential for safe design.

Termination Efficiency

How a wire rope is terminated has a significant impact on the usable strength. No termination method achieves 100% of the rope's catalog breaking strength. Typical termination efficiencies include:

• Swaged fittings (machine-pressed): 90–95% efficiency — the highest for field-installable terminations. This is the recommended method for structural and safety-critical applications.
• Hand-spliced eye: 80–90% efficiency, depending on the number of tucks and the skill of the splicer.
• Wire rope clips (U-bolt type): 80% efficiency when properly installed with the correct number of clips, torque, and saddle orientation.
• Ferrule / crimp sleeves: 70–90% efficiency, highly dependent on the ferrule material, size, and pressing die.
• Simple knot or loop without thimble: as low as 50% efficiency — never acceptable for load-bearing applications.

Always factor termination efficiency into your WLL calculation. If you are using wire rope clips at 80% efficiency, the effective breaking strength of the assembly is only 80% of the catalog value, and the WLL must be reduced accordingly.

Bend Radius and Sheave Diameter

When wire rope passes over a sheave (pulley) or around a thimble, the wires on the outer side of the bend experience higher stress than those on the inner side. This bending stress adds to the direct tensile stress and reduces the rope's effective load capacity. The smaller the bend radius relative to the rope diameter, the greater the strength reduction.

As a general rule, the sheave diameter should be at least 20 times the rope diameter for 7x19 construction, 25 times for 7x7, and 35 times for 1x19. Using undersized sheaves not only reduces immediate strength but also dramatically accelerates fatigue failure over repeated bending cycles.

Temperature Effects

Stainless steel wire rope retains its full strength from cryogenic temperatures up to approximately 300 °C. Above this temperature, tensile strength begins to decrease progressively. At 400 °C, expect a 5–10% reduction; at 500 °C, roughly 20–30%. For applications involving sustained high temperatures, consult the wire manufacturer for specific derating curves. At the other extreme, austenitic stainless steels (304, 316) maintain excellent toughness and ductility down to –196 °C (liquid nitrogen temperature), making them well suited for cryogenic applications.

Corrosion and Wear

Corrosion reduces the effective cross-sectional area of individual wires, directly lowering the rope's breaking strength. Pitting corrosion is particularly dangerous because it creates local stress concentrations that can initiate fatigue cracks. External abrasion — from contact with sheaves, fairleads, or rough surfaces — similarly removes material and reduces strength. Regular inspection and timely replacement are the primary defenses. Choose 316 grade for marine and chemical environments, and consider PVC-coated rope where external abrasion is a concern. For more on grade selection, see our 304 vs 316 comparison guide.

Fatigue from Repeated Bending

Wire rope that runs over sheaves or oscillates under load will eventually fail from bending fatigue, even if the applied load never approaches the breaking strength. Fatigue life depends on the bend ratio (sheave diameter ÷ rope diameter), the load range, the number of cycles, and the rope construction. High-flexibility constructions like 7x19 inherently last longer under repeated bending than rigid constructions like 1x19. Design for fatigue by selecting the appropriate construction, maintaining adequate sheave diameters, and establishing a scheduled inspection and replacement program.

Working Load Limit Standards by Application

Every WLL calculation starts from the same formula — WLL = Minimum Breaking Force ÷ Safety Factor — but the safety factor itself is not a single universal number. It is set by the standard or regulatory body that governs your specific application, and it reflects how much risk that application can tolerate. A static architectural cable that fails causes an inconvenience; a personnel-carrying cable that fails can cause a fatality. The required margin scales accordingly.

Because the consequences of failure — not just the load itself — determine the required safety factor, you should never treat a rope's breaking strength as a target working load. A rope loaded anywhere near its breaking point offers no margin for shock loading, wear, or measurement error, and its remaining fatigue life drops sharply. For a deeper look at how these ratings are verified in practice, see our guide to wire rope testing methods and standards.

How Wire Rope Construction Affects Strength

Diameter is not the only variable that determines breaking strength — construction matters just as much. As the tables above show, a 6.0 mm rope ranges from 25.06 kN (7x19) to 36.36 kN (1x19), a difference of more than 45% at the exact same diameter. This gap comes down to the fill factor: the proportion of the rope's circular cross-section that is actually occupied by load-bearing steel, versus the interstitial gaps between wires and strands.

A 1x19 rope is a single strand of thick, straight wires, so it packs steel efficiently and reaches a breaking load factor of roughly 0.95. A 7x7 rope bundles seven small strands around a core, introducing more void space and a lower factor of about 0.88. A 7x19 rope, with 133 fine wires laid up in a more complex helical pattern, has the lowest fill factor of the three at approximately 0.85 — but that same construction is what gives it superior flexibility and bend fatigue life.

This creates a direct trade-off: strength-optimized constructions like 1x19 sacrifice flexibility, while flexibility-optimized constructions like 7x19 sacrifice some raw strength-per-diameter. If your application is static — standing rigging, balustrade infill, tension members — prioritize the higher fill factor of 1x19. If your rope needs to run over a sheave, spool onto a drum, or flex repeatedly — winch lines, control cables, running rigging — prioritize the flexibility of 7x19, and simply step up one diameter size if additional breaking strength is needed to compensate. For a full side-by-side breakdown of flexibility, bend radius, and fatigue life, see our 7x7 vs 7x19 construction comparison.

Quick Reference: What Reduces Wire Rope Breaking Strength

The tables at the top of this page are laboratory maximums for new, straight, correctly terminated rope. The table below summarizes how much of that strength you actually keep once the rope is installed and in service — use it alongside the detailed explanations in the section above.

Regular inspection is the only way to catch corrosion, wear, and fatigue damage before they become failures — see our wire rope inspection checklist for a complete 12-point program. If you are deciding between termination methods, our swaging vs crimping comparison covers strength, tooling, and cost in detail.

Breaking Strength by Material Grade

A common misconception is that 316 stainless steel wire rope is inherently stronger than 304, or that stainless steel is always stronger than galvanized. In reality, breaking strength is set by the wire tensile grade (typically 1570 MPa or 1770 MPa for stainless rope wire, and up to 1960 MPa for high-tensile galvanized rope wire) and by construction and diameter — not by the alloy itself. At the same tensile grade, 304, 316, and galvanized wire rope of identical construction and diameter share the same published minimum breaking force.

* Values for 1960 MPa grade are calculated by scaling the 1770 MPa figures using the MBF = d² × K × R relationship described earlier (breaking force scales linearly with tensile grade). Not every supplier offers 1960 MPa wire in every construction — confirm availability and get a test certificate before specifying. (Table shown for 7x19 construction.)

What actually differs between grades is corrosion resistance and how quickly a rope's in-service strength degrades: 316 resists chloride pitting far better than 304 in marine or de-icing-salt environments, while galvanized rope relies on a sacrificial zinc coating that corrodes preferentially but is eventually consumed. Choosing the right grade for your environment protects the breaking strength you paid for over the rope's service life, even though it doesn't change the day-one number. See our 304 vs 316 stainless steel guide and stainless steel vs galvanized comparison for full environmental and cost breakdowns.

Frequently Asked Questions

What is the breaking strength of 1/4 inch wire rope?

A 1/4 inch (6.0 mm) stainless steel wire rope has a minimum breaking force of approximately 27.15 kN (6,103 lbs) for 7x7 construction, 25.06 kN (5,633 lbs) for 7x19, and 36.36 kN (8,173 lbs) for 1x19 — all at the 1770 MPa tensile grade.

What is the breaking strength of 3/16 wire rope?

A 3/16 inch (5.0 mm) stainless steel wire rope has a minimum breaking strength of approximately 4,238 lbs (18.86 kN) for 7x7 construction, 3,912 lbs (17.40 kN) for 7x19, and 5,676 lbs (25.25 kN) for 1x19 — all at the 1770 MPa tensile grade.

What is the breaking strength of 1/8 inch wire rope?

A 1/8 inch (3.2 mm) stainless steel wire rope has a minimum breaking strength of approximately 1,735 lbs (7.72 kN) for 7x7 construction, 1,603 lbs (7.13 kN) for 7x19, and 2,327 lbs (10.35 kN) for 1x19 — all at the 1770 MPa tensile grade.

How much weight can a 3/8 wire rope hold?

A 3/8 inch (10.0 mm) 7x7 stainless steel wire rope has a minimum breaking strength of approximately 16,954 lbs (75.42 kN) at 1770 MPa grade. With the 5:1 safety factor required for general lifting, its working load limit is 3,390 lbs. For static architectural use at 3:1, the limit is 5,651 lbs.

What is the difference between breaking strength and working load limit?

Breaking strength is the force at which the rope will fail. Working Load Limit (WLL) is the maximum force the rope should be subjected to in normal use. WLL = Breaking Strength divided by a safety factor (typically 3:1 to 10:1 depending on the application).

Does wire rope construction affect breaking strength?

Yes. For the same diameter, 1x19 construction provides the highest breaking strength, followed by 7x7, then 7x19. However, 7x19 offers the most flexibility. Choose based on whether your application prioritizes strength or flexibility.

How does corrosion affect wire rope breaking strength?

A 10% loss of metallic cross-section area due to corrosion results in approximately 15% reduction in breaking strength. Regular inspection and choosing the correct material grade (316 for marine environments) is essential for maintaining rope integrity.

What safety factor should I use for wire rope?

General purpose rigging uses 3:1, overhead lifting requires 5:1 (per OSHA / ASME B30.9), personnel lifting requires 6:1 to 10:1, and elevator applications require 8:1 to 10:1. Always follow the applicable standard for your specific application.

Download Our Complete Specification Sheet

For a printable reference that includes breaking strength tables for all twelve constructions we manufacture — plus diameter tolerances, weight-per-meter data, and recommended sheave diameters — download our comprehensive product specification sheet:

Download: Qianjun Stainless Steel Wire Rope Catalog & Specification Sheet (PDF)

Need a custom specification or have questions about a specific application? Our engineering team can provide tailored breaking strength data, recommend the optimal construction and diameter, and supply test certificates for your project. Get in touch — we typically respond within 2 hours during business hours.