Understanding Stretch in Wire Rope and Cable


After determining the correct size wire rope or cable, many think they have taken all the necessary steps to buy the right product for their application. However, this is not the case! A commonly overlooked, but highly important factor when purchasing cable and wire rope is stretch. It is crucial to know about the two types of stretch (Structural and Elastic) and the formula for calculating stretch in cable. Continue reading to learn about the importance of stretch and how it is determined to ensure you get the right wire rope and cable for your application.

The Two Types of Stretch:

1. Structural Stretch:

Structural stretch is the lengthening of the lay in cable and wire rope construction as the individual wires adjust under load. While certain levels of this stretch may be required, it is possible for stretch to be entirely removed by applying a pre-stretching operation to cable or wire rope before shipment.

2. Elastic Stretch:

Elastic stretch is the elongation of individual wires under load. The elastic stretch of cable or wire rope can be determined by using the formula below:

Calculating Cable Stretch:

To calculate stretch, a formula can be applied. The formula is (E= (W x G) / D2). The values derived from this calculator are an approximation, and it is important to remember to keep your units of measure constant. The most common measurement for cable is inches.

Definition of Formula:

E: Elastic stretch as a % of length

W: Weight of load in lbs

D: Diameter of wire rope in inches

G: Stretch Factor

While weight and diameter are simple to determine, Stretch Factor (G) is a bit trickier. Thankfully, Strand Core provides a visual guide with different stretch factors for various wire rope constructions. For example, 1x7 302 SS wire rope has a stretch factor (G factor) of 0.0000735 while 1x7 Galvanized wire rope has a G factor of 0.00000661. Another example is 1x19 302 SS wire rope has a G factor of 0.00000779, and 1x19 Galvanized wire rope has a G factor of 0.00000698. To find the G factor of 7x7, 7x19, 6x19, 6x37, and 19x7 constructions, you can visit our guide here.


By understanding the two types of stretch and the formula for calculating stretch, you will know exactly how much stretch occurs in your cable or wire rope application. Even though it may seem daunting at first, determining the stretch for cable or wire in applications is critical in choosing the suitable cable or wire for the job, and it's easy with our helpful guides!

If you are looking for a place to buy wire rope or cable, look no further than Strand Core. Why buy with us? We carry various styles and sizes of cable and rope, our products are Manufactured in USA, and we can provide a custom configuration of materials and constructions that comply with various industry specifications. If you want to learn more, please visit our website here. If you have any questions, our team is happy to help! Reach out to us by email through sales@strandcore.com or by phone at 800-983-9926. 

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