Minimum Bending Radius for Conduit (NEC Chapter 9, Table 2)

What the rule says

Each conduit article says that bends must be made without damaging the conduit or effectively reducing its inside diameter, and that the radius of a field bend, measured to the centerline, must not be less than Chapter 9, Table 2. The table has two columns: one for bends made on one-shot and full-shoe benders, and a larger one for other bends.

The gap between the columns grows with size. At 1/2" both are 4"; at 2" it is 9 1/2" against 12"; at 4", 16" against 24". Follow the edition your area has adopted, and your inspector.

Measured to the centerline

The radius in the table runs from the center of the bend to the middle of the conduit, not to its inside face. If you measure the inside of a finished bend, add half the conduit’s outside diameter.

Why there is a minimum

• The conduit stays round. Bent too tight, the wall flattens or kinks, and the space for wire shrinks.
• The wire pulls more easily. Wire drags harder around a tight bend, and its insulation rubs harder on the inside of it.
• The conduit stays strong. A kinked or flattened wall is weak and should be cut out.

How benders meet it

On a bender, the shoe sets the radius: a bend made in the shoe for the conduit’s type and size follows the shoe’s centerline radius all the way round. Benders are built around the Table 2 radii, which is why the right shoe, used the way its maker says, is how most electricians meet the rule without measuring anything.

Follow the manufacturer’s instructions for each size. Some manuals say which groove or shoe to use for a size so the bend meets code. When in doubt, ask your inspector before you bend a whole job.

Segmented bends and sweeps

A segmented bend is a row of small shots spaced along the conduit. The spacing sets the overall radius, which is usually far larger than the table asks for, while each shot is made on the shoe.

Big cable and long pulls often call for sweeps well beyond the minimum. The table is a floor, not a goal.