# Minimum Bend Radius for Cable

## What is a Minimum Bending Radius?

A cable's minimum bend radius is the smallest radius a cable can bend without being damaged. Although a cable's minimum bend radius varies depending on the cable type and industry standards, a general radius measurement can be calculated with the formula:

Cable Outer Diameter x Cable Multiplier = Minimum Bend Radius

## Minimum Bending Radius for Unshielded Twisted Pair (UTP) Cable

According to the TIA/EIA-568 standards, the minimum bend radius for unshielded twisted pair (UTP) cable is 4 times the cable's diameter.

Example: A typical Cat cable has a diameter of 0.25 inches. Using the formula, 0.25" x 4 = 1", the bend radius must be at least 1 inch.

For multi-pair cables the minimum bending radius is 10 times outside diameter.

## Minimum Bending Radius for Shielded Twisted Pair (STP) Cable

The minimum bend radius for Type 1A Shielded Twisted Pair (100 Mb/s SRP) is 3 inches for non-plenum cable.
For the stiffer plenum-rated cable, the minimum bending radius is 6 inches.

## Minimum Bending Radius for Fiber Optic Cable

The minimim bend radius for fiber optic cables is 10 times its diameter.
When the fiber optic cable is under tension, such as being pulled, the bend radius is 20 times its diameter.

Note: The standard goes on to state that no optical cable will be bent on a radius less than 1.18 inches.

## 100 ohm and 120 ohm Balanced Cable

A different standard, ISO DIS 11801 (essentially a parallel standard to the one mentioned above) lists three different minimum bend radius:

• Minimum bend radius for pulling during installation is 8 times cable diameter.
• Minimum installed radius is 6 times for riser cable.
• Minimum installed radius is 4 times cable diameter for horizontal runs.

For fiber optical cables, the requirements are the same as those stated above.

Note: Manufacturers recommendations can differ from the above. For more accurate information, refer to the cable's spec sheet.

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Warning: When using this information to perform electrical work, call a licensed electrician and consult the NEC® for safety. All licensed electricians have passed examinations covering the National Electric Code®, know state and local building codes, and may carry insurance to cover damages.