Shrink is the length a bend “eats” from your conduit run. Bend an offset and the finished run comes up shorter than the straight stick you started with — by a predictable amount. Every coupling that lands in the wrong place on a rough-in can usually be traced back to shrink nobody accounted for.
The bent path between two marks is longer than the straight-line distance the bend covers. The difference is shrink. It is not the same as take-up (where the bend starts relative to your mark) or gain (developed-length consumed by the arc) — though all three shorten the finished run compared to the raw stick, which is why beginners mix them up.
| Bend angle | Shrink per inch |
|---|---|
| 10° | 1/16" |
| 15° | 1/8" |
| 22.5° | 3/16" |
| 30° | 1/4" |
| 45° | 3/8" |
| 60° | 1/2" |
Multiply by your offset height for total shrink.
Example 1 — simple offset. 6" offset at 30°: 6 × 1/4" = 1.5" of shrink. Cut the stick 1.5" long or the far coupling lands 1.5" off the box.
Example 2 — 4-point saddle. Two 4" offsets at 30° around a duct: shrink applies twice, once per offset — 2 × (4 × 1/4") = 2" total. Saddles surprise people because the doubling is easy to forget.
Example 3 — rolling offset. 6" rise, 8" roll at 30°: shrink applies to the true offset (√(36+64) = 10"), so 10 × 1/4" = 2.5" — not the 1.5" you would get from the rise alone.
Add up the shrink for every bend in the stick before you cut. One offset's 1.5" is a nuisance; three bends' worth across a long run is a miscut. The calculator totals shrink for you — including the doubled shrink on saddles and the true-offset shrink on rolling offsets — so the number you cut to is the number that lands.
Try it free: Open the free offset bend calculator — all six bend calculators, no sign-up.
Get Conduit Bend Calc on Google Play for bender calibration and Pro tools.