Segmented 90° bend calculator

When a 90 needs a bigger radius than any shoe or factory elbow, bend it in shots: several small, equal bends spaced along the conduit. The arc's developed length tells you how much conduit the sweep uses, and dividing it up tells you where each shot goes.

Last reviewed Nov 14, 2026 · Sources at the end of the page

The segmented 90 formulas

Developed length = (π ÷ 2) × radius ≈ 1.5708 × radius
Degrees per shot = 90 ÷ number of shots
Spacing = developed length ÷ number of shots

The developed length is a quarter of the circumference at the centerline radius — IBEW Local 903's Bending Book uses "multiply the radius by 1.57." It's the straight conduit the sweep consumes.

Worked example: 24″ radius, 6 shots

1. Developed length: 1.5708 × 24 = 37 11/16″.
2. Degrees per shot: 90 ÷ 6 = 15°.
3. Spacing: 37 11/16″ ÷ 6 = 6 5/16″.
4. Marks from the start of the sweep: 0″, 6 5/16″, 12 9/16″, 18 7/8″, 25 1/8″, 31 7/16″.

Two common spacing conventions

Dividing the developed length by the number of shots (what this calculator and the BendBoss app do) puts each shot at the middle of its share of the arc. Local 903's book divides by one less than the number of bends, so the first and last bends sit right at the ends of the arc — its example is a 4″ radius in 9 bends of 10°, 6.28″ ÷ 8 spaces ≈ ¾″. That spreads the sweep slightly wider. Either works; be consistent and check the finished radius against your layout.

How many shots?

More, smaller shots look smoother. Gardner Bender's guide caps hickey segment bends at 10° per bend, and Local 903 suggests keeping the spaces under about 3″ so the elbow stays smooth. Check the minimum bending radius for your conduit in NEC Chapter 9, Table 2.