Conduit Bending Calculator

How far apart are offset bends?

A conduit bending calculator works out where to put the two marks for an offset: distance between bends = offset depth ÷ sin(bend angle). For a 4 in offset at 30°, sin 30° is 0.5, so the marks go 4 ÷ 0.5 = 8 in apart. That pair of bends kicks the conduit sideways around a beam, box, or ledge and brings it back parallel to where it started.

The second number to know is shrink: the length the run loses because the conduit now crosses the offset on a diagonal. At 30°, plan on about ¼ in of shrink for every inch of offset, so a 4 in offset shrinks about 1 in.

The formula in plain words

Picture the conduit as the long side of a right triangle. The offset depth is the short side opposite the bend angle. Trigonometry says the long side equals the short side ÷ sin(angle).

1. Distance between bends = offset ÷ sin(angle). This number is also called the multiplier: offset × multiplier gives the same answer.
2. Shrink = offset × shrink per inch for that angle.
3. Where to mark: when bending toward an obstruction, measure to the obstruction, add the shrink, and make the first mark there. Then measure the bend spacing back from it for the second mark.

Worked examples

1. 4 in offset at 30° (calculator defaults)

• sin 30° = 0.5
• Distance between bends: 4 ÷ 0.5 = 8.00 in
• Shrink: 4 × ¼ = 1 in

If the obstruction starts 40 in from the end of the conduit, put the first mark at 41 in and the second at 49 in.

2. 6 in offset at 45° to clear a joist

• sin 45° = 0.707
• Distance between bends: 6 ÷ 0.707 = 8.49 in
• Shrink: 6 × ⅜ = 2.25 in

Compare a 6 in offset at 30°: the marks would sit 12 in apart and shrink would be 1.5 in. The 45° offset is shorter but pulls harder.

Multiplier and shrink by bend angle

Bend angle	Multiplier (1 ÷ sin)	Shrink per inch of offset	4 in offset: spacing	4 in offset: shrink
10°	5.76 (≈ 6)	1/16 in	23.0 in	¼ in
22.5°	2.61	3/16 in	10.5 in	¾ in
30°	2.00	¼ in	8.0 in	1 in
45°	1.41	⅜ in	5.7 in	1½ in
60°	1.15	½ in	4.6 in	2 in

These shrink values are the rounded figures printed in most bending guides. The multiplier column is for bend spacing only. Multiplying the offset by it does not give shrink.

How to measure for an offset

• Offset depth: measure from the face the conduit runs along to the face it needs to clear, at right angles to the run. Add any clearance you want.
• Distance to the obstruction: measure along the run from a fixed reference, such as the end of the stick or the last coupling.
• Bender marks: benders carry an arrow or notch for offsets. Line each mark up with the same reference both times, or the offset comes out uneven.
• Same plane: roll the conduit 180° between the two bends and keep it flat on the floor so both bends lie in one plane.

Common mistakes

• Using the multiplier as shrink. At 30°, the multiplier is 2 but shrink is only ¼ in per inch. Mixing them up on a 4 in offset throws the marks 7 in off.
• Forgetting shrink entirely. The conduit lands short of the box by the shrink amount.
• Too many bends in one pull. Every offset adds two bends to the run. Codes limit the total degrees of bend between pull points, so check yours before adding another offset.
• Measuring offset on a slant. Offset depth is the straight-out distance, not the diagonal.

Plan the rest of the run

Choose the raceway with the conduit size calculator and check that the wires fit with the conduit fill calculator. Long runs also need a voltage drop check. Electrical work is code-governed and safety-critical, so have the installation done or inspected by a licensed electrician under your local code.