MachineCalcs

Wire Rope Stretch Calculator

Estimate elastic stretch and optional constructional stretch for wire rope, cable or sailboat standing rigging from load, span, diameter, modulus and metallic area factor.

Structural 6 inputs 6 results
Used in Standing Rigging 6

Calculator

Inputs

View results
Load or initial tension applied to the wire rope.
lbf
Free length of wire rope used for the stretch estimate.
ft
Nominal wire rope diameter.
in
Effective axial modulus for the rope construction. Strand construction and lay reduce stiffness versus a solid bar.
Mpsi
Approximate fraction of solid round area occupied by metal in the strand construction.
Optional permanent/settling stretch allowance as a percent of length.
% length

Results

Default result
Edit inputs
Total stretch(delta_total)
0.6261in
Pass

Also computed

Elastic stretch(delta_e)0.2661in

Constructional stretch(delta_c)0.36in

Elastic strain(epsilon)0.07393%

Axial stiffness(k)2,818lbf/in

Estimated metallic area(A)0.03682in²

Method notes 3 notes
  • Elastic stretch uses delta = F*L/(E*A), with A estimated from nominal diameter and metallic area factor.
  • Constructional stretch is added as an optional length-percent allowance; use manufacturer rope data when available.
  • Standing rigging and lifting systems are safety-critical. Final wire rope selection, terminations, fatigue, corrosion, inspection intervals and rig tuning need qualified manufacturer or professional guidance.

Wire rope stretch is estimated from the axial relation delta = F*L/(E*A), where F is tension, L is span length, E is effective modulus and A is metallic area. This calculator estimates A from nominal rope diameter and metallic area factor, then adds optional constructional stretch as a percent of length to return total stretch and axial stiffness.

Continue workflow

All Structural
Workflow placement Standing Rigging Stage 2: Set load share, tension and stretch
Next 1 Set rigging tension Use stretch and axial stiffness context when standing rigging needs a target tension or take-up estimate. Next 2 Build rigging spec Carry stretch allowance into a replacement stay or shroud cut-length worksheet. Next 3 Check rigging wire Check breaking-strength safety factor separately from stretch and stiffness. Chart Use reference data Round section modulus formula

How to use this calculator

  1. Enter tension. Use the working tension or dockside initial tension being checked.
  2. Enter span and diameter. Use the free wire length and nominal rope diameter.
  3. Set stiffness inputs. Enter effective modulus and metallic area factor for the rope construction.
  4. Add constructional stretch. Use manufacturer data if available, or leave a small allowance for bedding-in.
  5. Review total stretch. Compare elastic, constructional and total stretch against the adjustment range or design target.

How it works

Wire rope elastic stretch follows the axial-bar relation: delta = F x L / (E x A) The calculator estimates metallic area from nominal diameter and the entered area factor, then adds optional constructional stretch as a percent of length.

For a sailboat standing rigging strength screen, use the standing rigging wire size calculator. For replacement stay or shroud cut length, use the standing rigging spec calculator. For round-section hardware checks, use the round section modulus reference or shaft diameter calculator.

Worked example

Verified against the live calculator

A 30 ft span of 1/4 in wire at 750 lbf tension, with an effective modulus of 190 GPa and 0.75 area factor, stretches about 0.266 in elastically. Adding 0.1% constructional stretch raises the total to about 0.626 in.

Frequently asked questions

How do you calculate wire rope stretch?

Elastic stretch is delta = F*L/(E*A), where F is tension, L is span length, E is effective modulus and A is metallic area.

What is metallic area factor?

Wire rope is not a solid round bar. The metallic area factor estimates how much of the nominal circular area is actually metal in the strand construction.

What is constructional stretch?

Constructional stretch is settling or bedding-in stretch from rope construction and lay. Enter a manufacturer value when available; otherwise use it as a rough allowance.

Can this size sailboat standing rigging?

No. Use this only for stretch. For breaking-strength screening use the standing rigging wire size calculator, and for real rigging use manufacturer data and a qualified rigger.

Method & assumptions

  • Elastic stretch uses the linear relation F*L/(E*A).
  • Metallic area is estimated from nominal diameter and area factor, not pulled from a rope catalog.
  • Constructional stretch is a separate allowance and may be near zero for pre-stretched or well-set rigging.
  • Standing rigging, lifting and safety systems require qualified manufacturer or professional guidance for final selection and inspection.
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