Conduit Shrink Calculator: Offsets, Saddles & Kicks

Updated 2026-09-29

Short answer: shrink = depth × shrink per inch (30° = 1/4", 45° = 3/8", 22.5° = 3/16", 10° = 1/16", 60° = 1/2"). Add it to your measurement when you bend toward an obstruction. For a 3-point saddle, move the center mark out by 3/16" per inch of depth (45° saddle).

What shrink is

When conduit climbs over an offset, the part between the bends travels diagonally. A diagonal is longer than the straight run it covers, so the finished piece reaches less far along the wall than the same length of straight pipe. That difference is shrink. If you ignore it, an offset measured to clear an obstruction lands short and hits it.

Shrink per inch of depth, by angle

Angle	Shrink per inch (rule)	Exact tan(θ/2)	6" offset	10" offset
10°	1/16"	0.087	3/8"	5/8"
15°	1/8"	0.132	13/16"	1-5/16"
22.5°	3/16"	0.199	1-1/8"	1-7/8"
30°	1/4"	0.268	1-1/2"	2-1/2"
45°	3/8"	0.414	2-1/4"	3-3/4"
60°	1/2"	0.577	3"	5"

Where to add shrink

Offset toward an obstruction: measure from the end of the conduit to the obstruction, add the shrink; that is where the offset must finish (the second mark).
Offset away from an obstruction: the first mark is where the offset starts; shrink does not change it, but the far end of the run comes up short by the shrink.
Kick: the kick mark stays put, and the end of the conduit lands the shrink closer than straight pipe would.

Shrink in saddles

3-point saddle	Center mark shift per inch	Total shrink per inch
45° / 22.5°	3/16"	3/8"
60° / 30°	1/4"	1/2"
90° / 45°	3/8"	3/4"

A 4-point saddle is two offsets, so it shrinks twice as much as one offset of the same depth. Only the first side moves the marks toward the obstruction; the second side shortens the run beyond it. See the 3-point and 4-point saddle calculators.

Rule of thumb vs exact shrink

The per-inch rules round the exact values down: 30° is 0.268 per inch, not 0.25. On a 6" offset the difference is about 1/8"; on a 10" offset at 45° it is 3/8" (4-1/8" exact vs 3-3/4" by the rule). A real bend on a shoe also saves a little conduit, which reduces the true shrink slightly. The formulas are on the formulas page.

When shrink does not matter

If nothing on the far side of the bend has to land at an exact spot, and you are not measuring to an obstruction, you can ignore shrink and cut the conduit long. It matters when an offset must clear something at a measured distance, or when a stick has to fit exactly between two boxes.

Questions electricians ask

How do you calculate conduit shrink?

Multiply the offset depth by the shrink per inch for your angle: 10° = 1/16", 22.5° = 3/16", 30° = 1/4", 45° = 3/8", 60° = 1/2". A 6" offset at 30° shrinks 1-1/2". The exact value is depth × tan(angle ÷ 2).

Do you add or subtract shrink?

Add it to your measurement when the offset or saddle is bent toward an obstruction measured from the end of the conduit. The bend uses up conduit, so the marks move out by the shrink.

Why is shrink different for a 3-point saddle?

A 3-point saddle is two half-angle slopes meeting at the center, so the center mark moves out by the shrink of one slope: 3/16" per inch of depth for a 45° saddle. The whole conduit shrinks twice that.

Does a 90 have shrink?

Not in the same sense. A 90 is marked with the take-up (deduct), and the conduit a 90 saves is called gain. Shrink applies to offsets, saddles and kicks.