Wire rope breaking force calculator

Calculation basis

F (kN) = K × d² × R / 1000

d: nominal diameter in mm; R: selected rope strength grade in N/mm²; K: construction-dependent factor. 1 kgf = 9.80665 N; 1 tf = 1000 kgf. Force units do not indicate an allowable suspended mass.

For 7×7 and 7×19, K is an approximate coefficient inferred from Deacon’s published tables; small differences from rounded table values are expected. For 6×36, K is published by CERTEX. For example, 7×7 at 4 mm / 1570 gives 9.747 kN versus 9.75 kN in the reference table. The 6×36 input range of 8–60 mm is a tool limit, not a certified product range. These are external reference values, not HTWR test results or a claim of product certification.

Parameter source

• SCIC · Construction coefficients / Table 1
• Lifting Gear Direct · 6×7 FC
• Rope Services Direct · 19×7
• Deacon · 7×7
• Deacon · 7×19
• CERTEX · 6×36 / technical guide

Scope and limitations

Applies to new, non-plastic-coated, non-compacted rope of the exact configuration shown. For coated rope, use the steel rope diameter, excluding the coating. Terminations, wear, corrosion, bending and dynamic loads are not included. Confirm the actual grade and certified breaking force with the manufacturer before use.

M indicates cross-lay wires; S indicates Seale and W indicates Warrington. 7×37M here means 6×37M-WSC. Added carbon-steel coefficients reference SCIC, Lifting Gear Direct and Rope Services Direct. Diameter ranges are calculator limits, not certification or stock availability. The grade of galvanised rope must be confirmed after coating; these coefficients do not apply to stainless variants automatically.