Rope Strength

How Do You Measure Rope Strength?

Each type of line, natural fibre, synthetic and wire rope, have different breaking strengths and safe working loads. Natural breaking strength of manila line is the standard against which other lines are compared. Synthetic lines have been assigned “comparison factors” against which they are compared to manila line. The basic breaking strength factor for manila line is found by multiplying the square of the circumference of the line by 900 lbs.

(900 lbs. X circumference 2 = breaking strength)

To calculate the breaking strength of synthetic lines you need to add one more factor. As mentioned above, a comparison factor has been developed to compare the breaking strength of synthetics over manila. Since synthetics are stronger than manila an additional multiplication step is added to the formula above.

(Comparison factor X 900 lbs. X circumference 2 = breaking strength)

Following is a comparison factor chart for synthetic lines:

Line Material Comparison Factor (greater than manila)
Polypropylene 1.4

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