How to Bend a Conduit Offset: Multipliers and Shrink
Multiply the offset depth by the angle's multiplier to get the distance between your two bend marks, and by the angle's shrink per inch to get how much the run shortens. At 30° the multiplier is 2 and the shrink is 1/4" per inch, so a 6" offset has marks 12" apart and 1 1/2" of shrink.
Multiplier and shrink chart
| Angle | Multiplier | Shrink per inch |
|---|---|---|
| 10° | 6 | 1/16" |
| 22.5° | 2.6 | 3/16" |
| 30° | 2 | 1/4" |
| 45° | 1.4 | 3/8" |
| 60° | 1.2 | 1/2" |
These are the rounded figures printed on most bender charts. They come from trigonometry: the multiplier is 1 ÷ sin(angle) and the shrink per inch is tan(angle ÷ 2). The exact 22.5° multiplier is 2.613 and 10° is 5.76; the rounding matters most on deep offsets.
How to bend an offset
- Measure the offset depth: how far the conduit has to move sideways, say 6".
- Pick the angle that fits the space. 30° is the usual choice.
- Work out the distance between bends: 6 × 2 = 12".
- Work out the shrink: 6 × 1/4 = 1 1/2".
- Make the first mark. Measure from the end of the conduit to where the offset must land, add the shrink, and mark it.
- Make the second mark 12" back toward the end of the conduit.
- Bend: make the first bend at one mark with the bender's arrow, then roll the conduit half a turn and make the second bend at the other mark to the same angle. Keep both bends in the same plane.
Offsets you'll bend often
| Depth | 22.5° | 30° | 45° |
|---|---|---|---|
| 2" | 5 3/16" / 3/8" | 4" / 1/2" | 2 13/16" / 3/4" |
| 3" | 7 13/16" / 9/16" | 6" / 3/4" | 4 3/16" / 1 1/8" |
| 4" | 10 3/8" / 3/4" | 8" / 1" | 5 5/8" / 1 1/2" |
| 6" | 15 5/8" / 1 1/8" | 12" / 1 1/2" | 8 3/8" / 2 1/4" |
| 8" | 20 13/16" / 1 1/2" | 16" / 2" | 11 3/16" / 3" |
| 12" | 31 3/16" / 2 1/4" | 24" / 3" | 16 13/16" / 4 1/2" |
Common mistakes
- Forgetting the shrink when bending into an obstruction, so the offset lands short.
- Dog-legging the second bend. If the conduit isn't rolled exactly half a turn, the two bends aren't in the same plane.
- Mixing the 22.5° multiplier. 2.6 is the chart value; some charts print 2.61. On a 12" offset the difference is about 1/8".
- Ignoring the total degrees in the run. Each offset adds two bends' worth of degrees toward the code limit between pull points.
Bender charts, springback and shoe radius differ between makes. Check your bender's own markings and make a test bend on scrap when it matters.
Questions
What is the multiplier for a 30 degree offset?
2. Multiply the offset depth by 2 for the distance between bends: a 4-inch offset has marks 8 inches apart. The exact value is 1 ÷ sin 30° = 2.
What is the shrink for a 30 degree offset?
About 1/4 inch per inch of offset depth. A 6-inch offset at 30° shrinks 1 1/2 inches.
Which angle should I use?
Shallow angles (10° or 22.5°) are easy to pull wire through but need a long run. 30° is the common default. 45° and 60° fit tight spaces but are harder pulls; the total degrees of bend in a run are limited by code.
When do I add the shrink?
When you're bending toward an obstruction, so the offset has to land at a measured point. Working away from a fixed point, shrink doesn't affect where the offset lands.