FabLayout

Conduit offset from the end calculator

Enter the offset depth, the bend angle and the distance from the pipe end to the bend that has to land on a fixed point. You get both marks measured from the end of the pipe.

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Enter your measurements

Export from the Truemark app

The PDF cut sheet with this drawing and your marks is made in Truemark. It works offline on site and keeps your jobs.

App StoreGoogle Play
Mark 1Mark 13636″″Mark 2Mark 24848″″Mark spacingMark spacing1212″″
Scale drawing

First mark from the end

36in

Exact geometry

Second mark from the end
In the app
Distance between marks
In the app
Shrink
In the app

Every result is in Truemark

The free web version shows the main result and the drawing. Truemark gives you every mark and measurement, and exports a cut sheet. It is free to download.

App StoreGoogle Play

How to lay it out

  1. Decide which bend is fixed

    Pick the bend that must land at a set distance: the near bend, closest to the pipe end, or the far bend, where the offset has to clear an obstruction or meet a box.

  2. Measure from the pipe end

    Square the end of the conduit and measure from it to where that bend has to sit. Enter it as the distance from pipe end.

  3. Mark both bends from the end

    Measure the first mark and the second mark from the same end and wrap each mark right around the pipe. For the far bend the shrink is already added.

  4. Bend the offset

    Bend at the first mark, roll the conduit 180° and bend at the second mark to the same angle, keeping both bends in one plane.

Good to know

  • FabLayout runs the same code as Truemark; the result is exact geometry.
  • Source: Greenlee Textron, Site-Rite Hand Bender Instruction Manual, IM 1071 Rev 4, offset table, p. 5 (offset geometry); the end reference is the same calculation as the Truemark app

Method and formula

This is an ordinary offset with the marks counted from the end of the pipe instead of from each other. The geometry does not change; only the reference moves.

  • Distance between marks = offset depth ÷ sin θ.
  • Shrink = offset depth × tan(θ ÷ 2).
  • Near bend fixed: the first mark is the distance you measured, and the second mark is one distance between marks further along.
  • Far bend fixed: second mark = distance + shrink, first mark = second mark − distance between marks.

The shrink only moves the far case. The pipe shortens as the first bend is made, so on the straight pipe the marks sit one shrink further from the end than the point you measured on the finished run. The near bend is made before any shrink happens, so its mark stays where you measured.

Worked example

The page defaults: a 6″ offset with 30° bends, the near bend 36″ from the end. The marks are 6 ÷ sin 30° = 12″ apart, so the first mark is at 36″ and the second at 48″. The shrink is 1.6077″. Switch the fixed bend to the far one and both marks move one shrink further along the pipe.

Questions

When does the far bend need to be fixed?

When the offset has to finish at a known point, such as the edge of a box, a knockout or the far side of an obstruction. Measuring the far bend from the end without the shrink leaves the offset short by the shrink.

Do I still need to cut the pipe long?

No. Both marks are measured from the end you squared, so you can bend from a cut end without trimming afterwards. Measure from that same end for every mark.

Why does the near case ignore the shrink?

Shrink happens in the length of pipe between the two bends and beyond. The near bend is the first one made, so nothing has shortened between it and the end yet.

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