When you bend a cable to a certain point, you risk damaging the internal wires that transmit signals through it. Although you may get away with bending an electrical cable slightly beyond its minimum bending radius, you might not have the same luck with network cables and other types of data-transmitting media that have each wire designated for a purpose. If one wire breaks in these cables, you lose the entire cable in many cases.
Measure the diameter of the cable with a precise tape measure. You usually may find the cable diameter on a label written by the manufacturer or written on the cable itself. If you get a radius, multiply it by two to calculate the diameter.
Determine the type of cable you use. The type of cable determines how much stress it can handle. A multiple conductor cable with individual shielding for each conductor requires different bending radius calculations than a fibre optic (networking) cable.
Multiply the cable diameter with the overall cable diameter multiple for its cable type. Fibre optic cables must not bend at a radius of less than 20 times their diameters, generally. Multiple conductor cables with shielding for each individual conductor must not bend at a radius of less than seven times their diameters. Multiply this number by two to get the minimum diameter they may bend around. See the Resources for a table with more minimum bending radii.
Bending a cable at a radius smaller than its minimum bend radius causes excessive stress exerted on the cable itself, damaging the internal wiring in some cases and causing unnecessary kinks in the cabling.