Parallel Roll Offset Chart

Use this parallel roll offset chart after the calculator result to document true diagonal offset, bend plane rotation, mark spacing, shrink, and final alignment checks.

Open calculator

Quick reference table

A rolling offset moves conduit in two directions at once, so spacing is based on the diagonal true offset rather than only the rise or side movement. The calculator combines horizontal and vertical offsets, applies the selected bend multiplier, and reports the roll angle needed to rotate the bend plane. Use this chart to keep rotation direction, mark spacing, and shrink tied together before bending.

Rolling offset examples at 30 degrees

Rolling offset examples at 30 degrees
Horizontal	Vertical	True offset	30 deg mark spacing
3 in	3 in	4.243 in	8.486 in
6 in	4 in	7.211 in	14.422 in
8 in	6 in	10.000 in	20.000 in
12 in	5 in	13.000 in	26.000 in

Roll direction field checks

Roll direction field checks
Check	Why it matters	Worksheet note
Horizontal direction	Left and right can reverse after flipping conduit	Mark roll direction with an arrow
Vertical direction	Rise versus drop changes the bend plane	Record up or down movement
Bender rotation	Wrong roll sends the second bend away from target	Write roll angle and rotation side
Support clearance	Diagonal movement can hit rack or wall space	Check both targets before bending

Formula basis

True offset = sqrt(horizontal offset^2 + vertical offset^2). Roll angle = atan2(horizontal offset, vertical offset). Mark spacing = true offset x multiplier.

Horizontal offset is the side-to-side movement of the conduit centerline.
Vertical offset is the rise or drop of the conduit centerline.
True offset is the diagonal movement used for mark spacing and shrink.
Roll angle is the rotation of the bend plane from vertical toward the horizontal offset.

Worked examples

6 inch by 4 inch rolling offsetTrue offset = sqrt(6^2 + 4^2) = 7.211 inches. At 30 deg, mark spacing is 7.211 x 2.0 = 14.422 inches before shrink and roll direction are recorded.

8 inch by 6 inch roll with a known diagonalAn 8 inch horizontal move and 6 inch rise create a 10 inch true offset. At 22.5 deg, spacing is about 26 inches using the 2.6 multiplier.

Assumptions. Balanced load and line-to-line voltage assumptions behind this chart.

The chart assumes the same bend angle is used for both bends in the rolling offset.
Roll angle and mark spacing depend on the chosen measurement reference and actual conduit path.
Finished alignment depends on bend plane rotation, conduit support, obstruction clearance, and the order used to transfer marks.

Code and standard notes. Planning limits that should be checked before final equipment selection.

Use this as a field planning worksheet and verify bend plane, bender rotation, conduit support, clearance, and final alignment on site.

How to use this chart

1Record both offsetsWrite horizontal and vertical movement from the calculator result before using any multiplier row.

2Use true offset for spacingApply the selected bend multiplier to true offset, not to only one leg of the movement.

3Label roll directionDocument roll angle, up or down movement, and left or right movement so the second bend is made in the intended plane.

Worksheet checklist. Record source basis, review gaps, and assumptions before using the chart result.

Record true offsetDocument the diagonal offset, selected angle, multiplier, and shrink allowance beside the calculator mark-spacing result.
Record mark locationsWrite first mark, second mark, roll angle, bend direction, and bender reference before field transfer.
Record alignment checksNote whether the finished conduit met both horizontal and vertical targets after the rolling offset was bent.

Common mistakes to avoid. Review these before turning chart current into an equipment decision.

Calculating mark spacing from vertical offset alone and underestimating the rolling offset length.
Rotating the conduit in the wrong direction between bends, which sends the second bend away from the target path.
Recording roll angle without also marking whether the conduit rolls left or right from the installer position.

Frequently asked questions

These answers explain how to use the chart without turning a quick reference into a final design decision.

Why use true offset instead of vertical offset?

The conduit moves diagonally in space, so mark spacing and shrink follow the combined horizontal and vertical offset.

What does the roll angle describe?

It describes how far the bend plane rotates so the conduit moves toward both the horizontal and vertical targets.

What is the most common field error?

Using the correct spacing but rotating the conduit in the wrong direction, which sends the offset away from the intended target.