Rope & Cordage by Size (Diameter)

Choose rope by diameter, material and length

Diameter is the width across a rope; circumference is the distance around it. A product labeled 1/8 inch × 50 feet supplies a nominal 1/8-inch diameter and a 50-foot cut length.

Use the conversion table below to compare units. A manufacturer's nominal rope size may differ from an exact mathematical conversion. Measure and select according to the product specification, especially when rope must fit hardware.

Inch-to-millimeter conversions

Diameter in inches Equivalent millimeters
1/16 1.59
1/8 3.17
3/16 4.76
1/4 6.35
5/16 7.94
3/8 9.52
7/16 11.11
1/2 12.70
5/8 15.88
3/4 19.05
7/8 22.22
1 25.40
1-1/4 31.75
1-1/2 38.10
2 50.80
3 76.20

Two ropes of one diameter can perform differently

Compare fiber composition, construction and the exact option's specifications. Diameter alone does not establish a working load rating. Read our guide to breaking strength and working load before using performance figures.

Plan the cut length

Allow enough length for knots, splices and finishing. For a craft pattern, confirm both diameter and strand construction before substituting a different cord. Explore rope and cordage by material, construction and project.

Choose rope by diameter and project

Start with the diameter and length your project calls for. These product links open specific sizes, so you can check the selected option before adding it to your cart.

Compare materials, diameters and lengths in our Rope & Cordage collection.