Parallel Offset Calculator

A parallel offset is a pair of bends used to shift a conduit run laterally around an obstruction while keeping the run parallel to its original centerline. When multiple conduits run side by side — a common condition in feeder risers, panel stub-ups, and rooftop racks — each conduit needs its own offset, but the bend marks cannot be identical. Because each conduit sits at a different center-to-center spacing from the reference conduit, its bend point must be shifted along the run, or the conduits will collide or fan out unevenly through the offset. The Parallel Offset Calculator produces the exact stagger distance and mark locations needed to keep a group of conduits parallel and evenly spaced through the bend.

Inputs and Their Field Role

The calculator uses five fields, each tied directly to a bending measurement taken at the conduit or on the layout table:

• Offset rise — the vertical or lateral displacement the conduit must clear, measured conduit-to-conduit on the straight runs. Clearance to an obstruction is not included here; it is added separately if required.
• Bend angle — the angle of one bend in the offset pair (not the total angle change across both bends). A 30° entry means each bend in the pair is 30°.
• Center-to-center spacing — the spacing between adjacent parallel conduits, measured in the plane of the bend.
• First conduit first mark — the distance from the conduit end to the first bend mark on the reference conduit, the conduit against which all others are staggered.
• Number of conduits — the count of conduits in the parallel offset group, including the reference conduit.

Formula and Calculation Logic

Travel is the straight-line distance between the two bend marks on a single conduit, measured along the conduit:

\(\text{Travel} = \frac{\text{Offset rise}}{\sin(\text{Bend angle})}\)

The offset multiplier is the constant multiplier associated with the bend angle, equal to \(1/\sin(\text{Bend angle})\). It converts rise directly to travel without recalculating the sine each time, matching the multiplier values used on standard bender travel tables (10° → 6, 22.5° → 2.6, 30° → 2, 45° → 1.4, 60° → 1.2).

The adjacent first-mark stagger is the shift in mark position between one conduit and its neighbor, driven by the half-angle relationship between spacing and bend angle:

\(\text{Stagger} = \text{Center-to-center spacing} \times \tan\left(\frac{\text{Bend angle}}{2}\right)\)

This half-angle form comes from the geometry of two conduits bent at the same angle but offset by a fixed lateral spacing: the mark shift needed to keep both conduits parallel through the bend is proportional to the tangent of half the bend angle, not the full angle.

Each subsequent conduit’s first mark is built by adding the stagger cumulatively from the reference conduit:

\(\text{Conduit}_n \text{ first mark} = \text{First conduit first mark} + (n-1) \times \text{Stagger}\)

The second mark on any conduit is simply its first mark plus the travel distance.

Calculation Example

With an offset rise of 4 in, a bend angle of 30°, a center-to-center spacing of 2 in, a first conduit first mark of 24 in, and a conduit count of 3:

Value	Result
Travel between marks	8 in
Offset multiplier	2×
Adjacent first-mark stagger	0.5359 in
First conduit first mark	24 in
First conduit second mark	32 in
Last conduit first mark	25.0718 in

Travel checks out as 4 in ÷ sin(30°) = 4 ÷ 0.5 = 8 in, consistent with the 2× multiplier at 30°. The stagger of 0.5359 in comes from 2 in × tan(15°) = 2 × 0.26795. The last conduit (conduit 3) first mark is 24 in + 2 × 0.5359 in = 25.0718 in, reflecting two stagger increments from the reference conduit to the outermost conduit in the group of three.

Field and Layout Limitations

The result assumes both bends in each offset pair use the same bend angle and that spacing between conduits stays constant through the bend plane — if spacing changes (e.g., conduits fan out before the offset), the stagger figure no longer applies uniformly across the group. The calculator does not account for bend radius, deduct length, or shrink, which affect where the mark falls relative to the bender’s arrow and must be applied per the bender’s own travel and shrink specifications for the conduit size in use. It also does not verify that the resulting bend radius or spacing satisfies raceway support spacing or bending space requirements at boxes and cabinets; those clearances must be checked against the applicable code requirements and verified by the installer or AHJ before the group is bent. Field marks should be laid out on the reference conduit first, then transferred to adjacent conduits using the stagger value, with a tape check across all conduits before bending to confirm the group remains square and parallel.