Conduit BendingBy Blissom · Updated 2026-10-23
Layout values: check them against your own bender, on scrap first.
Short answer: degrees per shot = 90 ÷ number of shots. Developed length = 1.571 × radius. Mark spacing = developed length ÷ shots. Put the first mark half a spacing past the start of the curve and measure every later mark from that same start point. These are geometric layout values: check them against your bender.
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 each shot at its distance from that start point (the calculator lists them). Measuring every mark from the start keeps rounding from adding up.
- 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. The sweep counts 90° toward the 360° limit between pull points.
Mark spacing table
| Radius | 5 shots (18°) | 9 shots (10°) | 10 shots (9°) | 15 shots (6°) | Developed |
|---|---|---|---|---|---|
| 12" | 3-3/4" | 2-1/8" | 1-7/8" | 1-1/4" | 18-7/8" |
| 18" | 5-5/8" | 3-1/8" | 2-13/16" | 1-7/8" | 28-1/4" |
| 24" | 7-9/16" | 4-3/16" | 3-3/4" | 2-1/2" | 37-11/16" |
| 30" | 9-7/16" | 5-1/4" | 4-11/16" | 3-1/8" | 47-1/8" |
| 36" | 11-5/16" | 6-5/16" | 5-5/8" | 3-3/4" | 56-9/16" |
| 48" | 15-1/16" | 8-3/8" | 7-9/16" | 5" | 75-3/8" |
The two layout methods
The developed-length method spaces the shots evenly along the ideal arc, and it is the one segment-bender manuals such as Greenlee's use. The tangent method treats the shots as the corners of a polygon whose sides touch the arc; its spacing is a little longer. The difference depends on the radius and the number of shots and grows with fewer shots and larger radii: at a 24" radius in 9 shots it is about 0.01", at a 48" radius in 5 shots about 1/8" per interval. Neither accounts for the radius of the shoe that makes each shot, so check the sweep as you go.
Spacing from developed length (the exam method)
Apprentice tests usually give the developed length instead of the radius and ask for the spacing between shots: developed length ÷ number of shots. A 60" developed length in 15 shots is 4" between shots, 72" in 12 shots is 6". The tangent-method figure is shown in brackets for comparison.
| Developed length | 9 shots | 10 shots | 12 shots | 15 shots |
|---|---|---|---|---|
| 36" | 4" (4.010") | 3-5/8" (3.607") | 3" (3.004") | 2-3/8" (2.402") |
| 48" | 5-5/16" (5.347") | 4-13/16" (4.810") | 4" (4.006") | 3-3/16" (3.203") |
| 60" | 6-11/16" (6.684") | 6" (6.012") | 5" (5.007") | 4" (4.004") |
| 72" | 8" (8.020") | 7-3/16" (7.215") | 6" (6.009") | 4-13/16" (4.804") |
| 90" | 10" (10.025") | 9" (9.019") | 7-1/2" (7.511") | 6" (6.005") |
To go the other way, the radius behind a developed length is R = developed length ÷ 1.571, so a 60" developed length is a 38.2" radius. Worked versions of these questions are on the exam questions page.
Worked example: a 30" radius sweep in 10 shots
- Degrees per shot: 90 ÷ 10 = 9°.
- Developed length: π ÷ 2 × 30 = 47.12", about 47-1/8". Spacing: 47.12 ÷ 10 = 4.71", about 4-11/16".
- Marks from the start of the curve, each worked out from the start and rounded on its own: 2-3/8", 7-1/16", 11-3/4", 16-1/2", 21-3/16", 25-15/16", 30-5/8", 35-5/16", 40-1/16", 44-3/4".
- The ideal 90° arc is 47-1/8" long. A segmented bend approximates that curve, and its actual material length depends on the layout method and the bender, so do not use it alone as an exact cut length.
These are geometric layout estimates, not a check that a particular conduit and bender can make the sweep. Check the conduit type and size, the shoe's actual radius, the room between shots and the maker's instructions; the NEC minimum bend radius (Chapter 9, Table 2) applies to the actual bends.
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.
Sources: NEC 2023: 358.24(A) (EMT bends; minimum centerline radius from Chapter 9, Table 2, one-shot and full-shoe column) and 358.24(B) (360° between pull points); other raceways follow their own bending sections; Standard trigonometry for developed length and shot spacing (see the formulas page). Method.
Questions electricians ask
How many shots for a segmented 90?
Enough that each shot is 10° or less for a smooth-looking sweep: 9 shots of 10° is a common choice. Fewer, larger shots are quicker to lay out but give a more visibly segmented sweep. How hard the wire pulls depends on the actual bend radii, the conduit and conductors, and the whole run, not on the shot count alone.
How do you calculate spacing for a segmented bend?
Divide the developed length by the number of shots, the method segment-bender manuals use: a 24" radius has a developed length of 37.70", so 9 shots are 4.19" (about 4-3/16") apart. The tangent method, 2 × radius × tan(degrees per shot ÷ 2), gives a slightly larger figure, 4.20" here.
What is the developed length of a 90?
The length of an ideal circular 90° arc: radius × π ÷ 2, about 1.571 × the radius. A 24" radius gives 37-11/16". A segmented bend only approximates that arc, so treat it as a layout figure rather than an exact cut length.
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
- Offline, saved as jobs
Android only. There is no iPhone version yet; the free calculators on this site work on any phone.
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