Conduit Bending Multipliers & Offset Shrink Chart
Bending · The math · Updated 2026-07-10
Offset multipliers convert an offset depth into the distance between your two bend marks: distance = depth × multiplier. The shrink constant tells you how much shorter the run gets, so your pipe still lands on the box.
Here's the chart every apprentice tapes inside a hard hat - and the reason the numbers are what they are.
Offset multiplier and shrink chart
| Bend angle | Multiplier | Shrink per inch of depth |
|---|---|---|
| 10° | 6.0 | 1/16" |
| 22.5° | 2.6 | 3/16" |
| 30° | 2.0 | 1/4" |
| 45° | 1.4 | 3/8" |
| 60° | 1.2 | 1/2" |
Worked example: 4" offset at 30°
- Distance between marks: 4" × 2.0 = 8".
- Shrink: 4" × 1/4" = 1" - so if the obstruction starts 40" out, put the first mark at 41", then the second 8" past it.
- Bend both marks to 30° in the same plane, second bend flipped 180° on the bender.
Why is 30° the crowd favorite? The multiplier is exactly 2 - doubling a number on a ladder beats multiplying by 2.6 - and the shrink is a clean 1/4" per inch. Shallower angles (10°) pull easier through long runs; steeper angles (45-60°) fit tight quarters but shrink more and pull harder.
Where the multipliers come from
The multiplier is the cosecant of the bend angle: 1 ÷ sin(θ). At 30°, sin = 0.5, so the multiplier is exactly 2.0. At 45°, 1 ÷ 0.707 ≈ 1.414 - rounded to 1.4 in the field. The published shrink constants are field-rounded, too; that's fine at hand-bend tolerances, but stacked offsets and long parallel runs accumulate the rounding error.
Exact marks instead of memorized constants
The app's bending calculator uses the exact trigonometry (not the rounded constants), then rounds the final tape marks to 1/16" - the only place rounding belongs. Pick the angle, enter the depth, and read the marks with the shrink already applied, for any of 11 bend types. The step-by-step bending guide shows the full workflow.
Multipliers, shrink, and marks - computed, cited, tape-ready. Conduit Fill & Bending Calc handles offsets, rolling offsets, saddles, kicks and 90s with exact math and your bender's real deduct. Free on the App Store. Download Conduit Fill & Bending Calc on the App Store.
Frequently asked questions
What is the multiplier for a 30 degree offset?
2.0 - the cosecant of 30°. Distance between marks = offset depth × 2. Shrink is 1/4" per inch of depth. A 5" offset at 30° means marks 10" apart and the run shrinks 1-1/4".
What does shrink mean in conduit bending?
An offset makes the pipe travel a diagonal, so the end of the conduit effectively pulls back toward the start. Shrink is that loss of run length. You add it to your measurement before the first mark so the far end still reaches the box.
How do I calculate a rolling offset?
Take the square root of rise squared plus roll squared to get the true offset depth, then use the normal multiplier for your angle. Example: 6" up and 8" over = √(36+64) = 10" true depth; at 30° the marks land 20" apart.
Which offset angle should I use?
30° is the default: multiplier of exactly 2, moderate shrink, easy pull. Use 10° or 22.5° when wire pull tension matters on long runs, and 45-60° only where space forces it - steeper angles shrink more and pull noticeably harder.