Offset Multiplier Chart and Shrink: How to Bend an Offset in EMT
An offset is two equal bends in opposite directions that move the pipe over without changing its direction. You need two numbers to lay one out: the distance between the marks (offset depth × the multiplier) and how much the pipe comes up short (the shrink). Both depend only on the bend angle.
None of this is in the NEC. It’s right-triangle trigonometry, the same method Benfield’s Conduit Bending teaches and Ugly’s Electrical References tabulates, and the numbers below are computed by the engine behind the Conduit Bending calculator.
Offset multiplier chart
Distance between marks = offset depth × multiplier. The multiplier is the cosecant of the bend angle (1 ÷ sin θ).
| Bend angle | Multiplier | Shrink per inch of offset |
|---|---|---|
| 10° | 5.759 | 0.087 in |
| 22.5° | 2.613 | 0.199 in |
| 30° | 2.000 | 0.268 in |
| 45° | 1.414 | 0.414 in |
| 60° | 1.155 | 0.577 in |
The numbers most people carry in their heads (6, 2.6, 2, 1.4, 1.2) are these rounded. Only the 30° one is exact. The 10° “×6” is really ×5.76, so a 6 in offset laid out at ×6 puts the marks 1.45 in too far apart, and the offset comes out deeper than you wanted.
Picking the angle
Use 30° unless something stops you. The multiplier is a clean 2, the shrink is small, and a pair of 30s costs 60° of the 360° allowed between pull points (358.26 for EMT).
Go to 22.5° when the run already has bends in it or the wire is big. The pull is easier and two 22.5s cost only 45° of that budget, at the price of marks that sit further apart.
Go to 45° when there isn’t room for a 30. The offset is shorter, but two 45s cost 90° and you’ll feel them on the pull. 60° is for very short offsets in tight spots.
10° is for shallow offsets, where a steeper bend would be too short to make. A box offset of ½ in at 10° puts the marks 2 7/8" apart with almost no shrink (1/16").
Shrink chart
The pipe shortens along the run because part of it now travels sideways. Rounded to the nearest 1/16 in, the way you’d mark it:
| Offset | 10° | 22.5° | 30° | 45° | 60° |
|---|---|---|---|---|---|
| 2 in | 3/16" | 3/8" | 9/16" | 13/16" | 1 1/8" |
| 3 in | 1/4" | 5/8" | 13/16" | 1 1/4" | 1 3/4" |
| 4 in | 3/8" | 13/16" | 1 1/16" | 1 11/16" | 2 5/16" |
| 6 in | 1/2" | 1 3/16" | 1 5/8" | 2 1/2" | 3 7/16" |
| 8 in | 11/16" | 1 9/16" | 2 1/8" | 3 5/16" | 4 5/8" |
| 10 in | 7/8" | 2" | 2 11/16" | 4 1/8" | 5 3/4" |
| 12 in | 1 1/16" | 2 3/8" | 3 3/16" | 5" | 6 15/16" |
The quarter-inch-per-inch rule for 30° is close. The exact figure is 0.268 in per inch: on a 10 in offset the rule says 2 1/2" and the real shrink is 2 11/16". On a 4 in box-to-box offset nobody will see the difference. On a long run lined up with other pipes, they will.
How to bend an offset in ½” or ¾” EMT
Example: a 4 in offset with 30° bends, to clear an obstacle whose face is 36 in from the end of the pipe.
- Measure the depth to the same face of the pipe at both ends. Bottom of the pipe to bottom of where it has to land, not centre to edge. Mixing faces adds a pipe diameter to the offset.
- Spacing. 4 in × 2.00 =
8"between marks. - Shrink. 4 in × 0.268 =
1 1/16". - Place the marks. You’re working toward the obstacle and the bends will pull the pipe back by the shrink, so add it: the mark nearer the obstacle goes at 36 in + 1 1/16" =
37 1/16"from the end, the other 8" back from that at29 1/16". Working away from a fixed point, with the offset at the start of the pipe, you don’t add shrink. - First bend. Line the mark nearer the end up with the arrow and bend to 30°, with heel pressure on the foot pedal so the pipe stays flat on the floor.
- Second bend. Roll the pipe exactly 180°, line the other mark up with the arrow, and bend to 30°. Sight down the pipe before you pull: if the first bend has rolled off vertical, you get a dog-leg you can’t fix by eye.
- Check it on the floor. The two straight legs should be parallel and the offset should measure 4 in.
The same offset at other angles: at 22.5° the marks are 10 7/16" apart with 13/16" of shrink; at 45° they’re 5 11/16" apart with 1 11/16".
The calculator is set to this example. Change the angle or the depth, or switch to Rolling for an offset that goes up and over at the same time.
8"
- Multiplier
- ×2.00
- Shrink
- 1.07 in
- Angle
- 30°
Multiplier = csc θ · bend geometry, not NEC
Lengths to scale; bend radius not drawn. Bend geometry from Benfield and Ugly's, not NEC.
Same bending math as the Voltkit app, with marks rounded to the nearest 1/16".
Show calculation
- Multipliercsc 30° = 1 ÷ sin 30°×2.000
- Between bends4.00 in × 2.0008.00 in
- Shrink4.00 in × (csc − cot) 30°1.07 in
Bend geometry: Benfield, Conduit Bending; Ugly's Electrical References. Stub take-up: standard hand benders. Not NEC.
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Saddles are offsets in disguise: the 3 point saddle bend guide picks up from here. Benders differ, so check yours and bend a test piece when the layout matters.
Every number in this guide is computed by the same engine as the Voltkit app. It cites NEC 2023 sections but doesn't reproduce NFPA text or tables; check the wording in your copy of the code and with your authority having jurisdiction.
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