Conduit offset calculator
An offset is two equal bends that jog a conduit over an obstruction and bring it back parallel. Enter the offset depth, the bend angle and — if you're working toward an obstruction — the distance to it. You get both marks, the distance between them and the shrink, in sixteenths.
Offset calculator
Marks are measured from the end of the conduit. Mark A is the bend nearest the obstruction (shrink added); Mark B is the distance between bends back toward the end. Multiplier is the exact cosecant of the angle.
The offset formula
Distance between bends = offset depth × multiplier
Multiplier = 1 ÷ sin(bend angle)
Total shrink = offset depth × shrink per inch
Mark A = distance to obstruction + total shrink
Mark B = Mark A − distance between bends
This is the procedure Greenlee, Klein Tools and Gardner Bender all print in their hand-bender guides: multiply the depth by the angle's multiplier for the spacing, multiply the depth by the shrink-per-inch value and add it to the distance to the obstruction. Gardner Bender's guide adds the rule that matters most in the field: shrink is only used when you are working into an obstruction, not away from it.
Worked example: 6″ offset at 30°, obstruction 20″ away
- Distance between bends: 6″ × 2.00 = 12″.
- Total shrink: 6″ × ¼″ per inch = 1 1/2″.
- Mark A: 20″ + 1 1/2″ = 21 1/2″ from the end.
- Mark B: 21 1/2″ − 12″ = 9 1/2″ from the end.
- Bend 30° at Mark A, roll the conduit 180°, bend 30° at Mark B. The finished offset reaches full height at 20″.
Multiplier and shrink at the common angles
| Angle | Multiplier (exact) | Shrink per inch of depth |
|---|---|---|
| 10° | 5.76 | 1/16″ |
| 22½° | 2.61 | 3/16″ |
| 30° | 2.00 | 1/4″ |
| 45° | 1.41 | 3/8″ |
| 60° | 1.15 | 1/2″ |
Choosing the angle
Greenlee's guide names the trade-off: a steeper angle needs more pulling force, a shallower angle needs more room. 30° is the everyday choice because its multiplier is a clean 2. 45° and 60° fit tight spaces but make the wire pull harder; 10° and 22½° are for small jogs where the run has room.
Shrink, in plain terms
Bending an offset uses up straight length — the conduit "shrinks" along the run. If you're bending toward something fixed (a box, a strut, an obstruction), add the shrink to your measurement so the offset still lands where you measured. If you're bending away from a fixed point, the shrink goes to the free end and you can ignore it.
Common questions
What is the multiplier for a 30° offset?
2.00. The multiplier is 1 ÷ sin(angle), and sin 30° is exactly 0.5, so a 30° offset needs twice the offset depth between bends — 12″ between marks for a 6″ offset.
How much does a 30° offset shrink?
¼″ per inch of offset depth, per Greenlee, Klein Tools and Gardner Bender. A 6″ offset at 30° shrinks 1½″.
Do I add shrink when I'm working away from the obstruction?
No. Gardner Bender's guide says shrinkage values are only used when working into objects, not away. Working away, the lost length ends up at the free end of the stick.
Which mark do I bend first?
Greenlee's guide starts at the mark nearest the obstruction (Mark A), rolls the conduit 180° and bends Mark B. Gardner Bender's guide bends the other mark first. Either works as long as both bends are the same angle and in the same plane.
Why does my bender say 6 for 10° when the calculator says 5.76?
Bender tables round the multiplier. The exact value is 1 ÷ sin 10° = 5.76. On a 2″ offset that's about ½″ of difference, so check what your bender's own scale assumes.
Sources
Every bend on this site, in one app
BendBoss does offsets, saddles, rolling offsets, stub-ups, kicks, parallel runs (mixed sizes), segmented and compound 90s — fraction keypad, bend diagrams and step-by-step walkthroughs. $25.00 once. No subscription, no ads. English and Spanish.
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