Conduit BendingUpdated 2026-09-29
Short answer: degrees per shot = 90 ÷ number of shots. Mark spacing = 2 × radius × tan(degrees per shot ÷ 2). The first mark is half a spacing past the start of the curve. Developed length = 1.571 × radius.
When to segment a 90
Hand benders make a 90 on a fixed radius of a few inches. When a run needs a larger radius (a big sweep into a panel, a large conduit on a mechanical bender, or a bend that has to match a curved wall), you make it from a series of small bends called shots.
How to bend a segmented 90
- Choose the radius of the sweep and the number of shots.
- Mark the start of the curve, then the first shot half a spacing past it, and every following shot one spacing apart.
- Bend each shot the same number of degrees, keeping the conduit from rolling between shots.
- Check the finished sweep against 90° and against the radius.
Mark spacing table
| Radius | 5 shots (18°) | 9 shots (10°) | 10 shots (9°) | 15 shots (6°) | Developed |
|---|---|---|---|---|---|
| 12" | 3-13/16" | 2-1/8" | 1-7/8" | 1-1/4" | 18-7/8" |
| 18" | 5-11/16" | 3-1/8" | 2-13/16" | 1-7/8" | 28-1/4" |
| 24" | 7-5/8" | 4-3/16" | 3-3/4" | 2-1/2" | 37-11/16" |
| 30" | 9-1/2" | 5-1/4" | 4-3/4" | 3-1/8" | 47-1/8" |
| 36" | 11-3/8" | 6-5/16" | 5-11/16" | 3-3/4" | 56-9/16" |
| 48" | 15-3/16" | 8-3/8" | 7-9/16" | 5" | 75-3/8" |
The formula
The shots form a polygon whose sides are tangent to the arc of radius R. Each side is 2R·tan(θ/2) long, so the marks sit at the corners of that polygon, and the first mark is half a side past the start of the curve.
Tips for a smooth sweep
- Draw a line along the conduit before you start and keep it on top, so the shots stay in one plane.
- Use a degree mark on the bender or a level for every shot rather than eyeballing.
- Under-bend the last shot slightly and check; it is easier to add a degree than to take one out.
Questions electricians ask
How many shots for a segmented 90?
Enough that each shot is 10° or less for a smooth sweep: 9 shots of 10° is the common choice. Fewer, larger shots (5 × 18°) are quicker but look faceted and pull harder.
How do you calculate spacing for a segmented bend?
Spacing between marks = 2 × radius × tan(degrees per shot ÷ 2). For a 24" radius in 9 shots, 2 × 24 × tan 5° = 4.2", about 4-3/16".
What is the developed length of a 90?
The length of conduit in the arc: radius × π ÷ 2, about 1.571 × the radius. A 24" radius 90 uses 37-11/16" of conduit.
Sweeps of any angle, nested on a rack
- Segmented bends of 30°, 45°, 60° or 90°, from the pipe end
- Concentric bends: every conduit on a rack with its own radius
- Developed length and gain for each conduit
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