Conduit BendingBy Blissom · Updated 2026-10-23
Layout values: check them against your own bender, on scrap first.
Short answer: true offset = √(horizontal² + vertical²). Use it as the depth of a normal offset. Make both bends in one plane, set atan2(horizontal, vertical) from vertical, toward the side the run moves over to.
What a rolling offset is
A rolling offset moves the conduit over and up (or down) at the same time: two equal bends made in a plane that is rolled between horizontal and vertical. It saves bends compared with an offset over followed by an offset up.
How to bend a rolling offset
- Measure both offsets: how far over (horizontal) and how far up (vertical).
- Find the true offset with the calculator or √(h² + v²).
- Lay out a normal offset of that depth with the multiplier and shrink for your angle (offset calculator).
- Make both bends in the same plane, at equal angles and in opposite directions, the way you bend any offset: Klein's offset method rotates the conduit 180° in the bender for the second bend. Do not twist the conduit into a different plane between bends.
- Set the roll: turn the finished offset so its plane sits at the roll angle from vertical, pointing at the target, or set up the bend with the conduit already in that plane.
The formula
Both offsets are entered as positive distances; the direction (left or right, up or down) is the side you point the offset toward. If both are zero, no offset is needed.
The box method in the field
Without a calculator, hold a square or tape at the start of the offset and measure diagonally from where the conduit is to where it needs to be: that diagonal is the true offset. Mark it on the floor or wall as a reference when rolling the conduit.
Worked example: over 8" and up 6" with 45° bends
- True offset: √(8² + 6²) = √100 = 10". Bend it as one 10" offset, not as two separate offsets.
- Distance between bends: 10 × 1.4 = 14". Shrink: 10 × 3/8" = 3-3/4".
- Roll: the offset's plane sits about 53.1° from vertical (atan2 of 8 and 6), toward the side the run moves over to.
- Make both opposing 45° bends in that one plane, then set the finished offset to the roll so it points at the target. The 53° roll is separate from the 180° turn in the bender for the second bend. Two bends add 90° toward the 360° limit, instead of four bends and 180°.
Mistakes
- Adding the two offsets instead of using the diagonal: 3" + 4" is not 7", it is 5".
- Twisting the conduit between the two bends, which puts them in different planes and gives a dog-leg instead of a clean offset.
- Measuring horizontal and vertical from different points on the pipe.
Sources: NEC 2023 358.24 and Chapter 9, Table 2; Klein Tools Conduit Bender Guide (stub take-up, offset multipliers and shrink, saddles). Method.
Questions electricians ask
How do you calculate a rolling offset?
Square the horizontal offset and the vertical offset, add them, and take the square root to get the true offset. Then use the true offset as the depth of a normal offset: distance between bends = true offset × multiplier, shrink = true offset × shrink per inch.
What is the roll angle?
The angle between the plane of the offset and vertical, so the offset moves over and up at the same time. With both offsets entered as positive distances, roll = atan2(horizontal, vertical); a 4" over by 3" up rolling offset rolls about 53° from vertical, toward the side it moves over to. With no vertical offset it is 90° (a flat offset), with no horizontal offset 0°.
Can I use the 3-4-5 rule for a rolling offset?
Yes. A 3" and 4" offset make a 5" true offset because 3² + 4² = 5². Any multiple works too: 6" and 8" make 10".
See the roll in 3D before you bend
- Isometric drawing of the rolling offset
- Both marks from the end of the pipe, with the obstruction distance
- Corrected for your bender shoe
- Parallel and matching offsets too
Android only. There is no iPhone version yet; the free calculators on this site work on any phone.
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