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Rolling offset in conduit: the formula, the roll angle and the marks

Square the vertical offset, square the horizontal, add them, square-root the total — that's your true offset, and you bend it like any other offset. 6" up and 8" over gives a 10" true offset, and at 30° that's 20" between bends with 2 11/16" of shrink. The Rolling Offset calculator (Pro) runs all four numbers and throws in the roll angle, which is the part that's easiest to get wrong doing it by hand.

3 min read · Updated 2026-09-10

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When you need a rolling offset

A rolling offset moves the pipe up and sideways in one move — off a rack onto a box that's both higher and further out. One tilted offset instead of two flat ones.

The rolling offset formula for EMT

  • True offset = √(vertical² + horizontal²).
  • Roll angle = arctan(vertical ÷ horizontal): how far the plane of the offset tilts from horizontal.
  • Distance between bends = true offset ÷ sin(bend angle), the usual offset multiplier.
  • Shrink = true offset × tan(bend angle ÷ 2).

PipeMaster works from the unrounded diagonal, not the fraction you see on screen. With 3" and 5", the true offset is √34 = 5.831", displayed as 5 27/32" — but the marks underneath are calculated from 5.831", so rounding twice doesn't creep in and throw your layout off by a sixteenth.

How to calculate a rolling offset in PipeMaster

  1. Open Rolling Offset under Pro Calculators.
  2. Pick the angle under Bend Angle: 10.0°, 22.5°, 30.0°, 45.0° or 60.0°.
  3. Enter the Vertical Offset and the Horizontal Offset, measured between the same faces of where the conduit is and where it has to go.
  4. Read True Offset, Roll Angle, Distance Between Bends and Shrink under Result.
  5. Mark and bend a normal flat offset with those two distances, then roll the finished piece into place so the offset plane sits at the roll angle.

Worked examples

PipeMaster results
Vertical OffsetHorizontal OffsetAngleTrue OffsetRoll AngleDistance Between BendsShrink
6"8"30°10"36.9°20"2 11/16"
3"4"45°5"36.9°7 1/16"2 1/16"
5"12"30°13"22.6°26"3 15/32"
3"5"30°5 27/32"31.0°11 21/32"1 9/16"

The first three rows are whole-number right triangles (3-4-5, 6-8-10, 5-12-13), handy for checking a tape measurement by hand. The last row is a typical real measurement.

Measuring for a rolling offset

Take both measurements at the same point along the run. Measure the rise with a level or plumb line, and the side-to-side distance square to the run, from the same face of the existing conduit to the same face of the target.

If the conduit also has to hit a fixed point along the run, add the shrink to that measurement before placing your first mark, exactly as with a flat offset.

Why not just bend two offsets?

Two separate offsets mean four bends. On EMT the total between pull points is capped at 360°, and every extra bend eats into that and makes the pull harder. A rolling offset does the same job in two bends, and honestly it looks a lot cleaner on a rack too.

Limits worth knowing

  • Only the five standard angles are available in the calculator.
  • The app gives distances, not the position of the first mark on the pipe.
  • Rolling Offset is part of PipeMaster Pro; the plain Offset calculator is free.

Questions and answers

What is the rolling offset formula for electrical conduit?
True offset = √(vertical² + horizontal²). Then multiply the true offset by the offset multiplier for your angle (2.000 at 30°) for the distance between bends, and by the shrink per inch (0.268 at 30°) for the shrink.
What does the roll angle tell me?
It is the tilt of the offset's plane from horizontal: arctan(vertical ÷ horizontal). For 6" up and 8" over it is 36.9°. You bend the offset flat, then rotate it by that much when you install it.
Is the rolling offset calculator free?
No, Rolling Offset is one of the Pro calculators. The free Offset calculator works if you first work out the true offset yourself with the formula above and enter it as the offset depth.

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