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How to Determine Bending Radius

Our customers occasionally ask us: “How tight can I get away with bending this cable?” when installing wire and cable in trays with curves, in ducts, around building corners or around sheaves. Bending radius information provided by the NEC (National Electric Code) and the Insulated Cable Engineers Association (ICEA) allows us to provide the following simple table to use as a guideline.

To use the table, obtain the cable diameter from either the manufacturer or by measuring the cable if you already have it. Then, simply multiply that diameter by the factor on the right side of the table.
Cable Type Bending Radius as a Multiple of
Cable Overall Diameter
Single or multi-conductor cable without metallic shielding
8 times the overall cable diameter
Single or multi-conductor cables with tape shielding
12 times the overall cable diameter
Multi-conductor cables with individually
shielded conductors.
12 times the individual cable diameter (pairs, triads, etc.) or
7 times the overall cable diameter. -- whichever is greater

For more precise information, see NEC Articles 300-34, 334-11 & 336-16, as well as Appendix H of ICEA S-66-524 and ICEA S-68-516. OR, simply contact your friendly Multi/Cable Sales or Engineering Associate.