Conduit Offset and Rolling Offset Calculator
Calculate standard and rolling-offset geometry, bend spacing, rotation, and theoretical shrink. New here? Read the quick guide.
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Conduit bending geometry
Configure the offset
Geometry preview
Two-bend offset
Bend angle is drawn to scale. Lengths are proportionally normalized to fit the preview.
How to mark and bend this configuration
Field instructions
Two-bend offset
Use the left end of the straight conduit as the starting end. Every measurement below begins at that same end—do not switch ends.
- Mark 1 from starting end
- 23.00 in (23 in)
- Mark 2 from starting end
- 47.00 in (47 in)
- Distance between marks
- 24.00 in (24 in)
- Both bend angles
- 30°
- 1Choose and label the starting end.
Lay the straight conduit in the direction it will be installed. Mark the left end START. All measurements begin at this end.
- 2Make Mark 1 at 23.00 in (23 in).
Measure from START and draw a clear line across the conduit. This mark includes the calculated common shrink allowance for the obstruction located at 20.00 in (20 in).
- 3Make Mark 2 at 47.00 in (47 in).
Measure from START again. As a cross-check, Mark 2 must be 24.00 in (24 in) beyond Mark 1.
- 4Bend Mark 1 to 30°.
Place the conduit in the bender and align the bender arrow exactly with Mark 1. Keep the offset plane indexed, move the handle in the first bend direction, and stop at 30°. Allow for normal springback.
Reference: arrow • First bend direction • Target: 30° - 5Turn the conduit over for Bend 2.
Rotate the conduit 180° around its long axis. Do not twist it onto a different bend plane. For a rolling offset, keep the same indexed rolling line at the bender reference.
- 6Bend Mark 2 to 30°.
Align the bender arrow exactly with Mark 2. Move the handle in the opposite bend direction and make the second bend to 30°.
Reference: arrow • Opposite bend direction • Target: 30° - 7Check the finished offset before installation.
Place the conduit against a flat reference. Confirm the two straight ends are parallel, the offset lands at the intended location, and there is no dogleg. Confirm the vertical rise. Correct or remake the bend if the measurements do not match.
Calculated result
Offset dimensions and formulas
Formula breakdown
True offset: 12 in
Multiplier: 1 ÷ sin(30°) = 2.0000
Ideal travel: 12.000 × 2.0000 = 24.000 in
Common field-table shrink: 12.000 × 0.2500 = 3.000 in
Exact geometric shrink: 12.000 × tan(15°) = 3.215 in
Export this offset calculation
Create a field worksheet containing the offset type, conduit, calculated geometry, bend marks, clearance checks, formulas, and manufacturer-neutral verification notes.
Conduit offset guidance
Use geometric results with the bender's instructions
A standard offset moves conduit in one plane. A rolling offset combines a vertical rise with a horizontal roll before applying the bend-angle multiplier. These formulas describe ideal centerline geometry; they do not replace tool-specific take-up, bend-radius, springback, or field-marking instructions.
What is the offset multiplier?
The multiplier is one divided by the sine of the selected bend angle. Multiply the true offset by this value to obtain the ideal centerline travel between two equal bends.
How is a rolling offset calculated?
The calculator combines vertical rise and horizontal roll using the Pythagorean theorem. It then applies the selected bend-angle multiplier to that true offset and calculates the rotation direction with atan2.
Is the calculated travel the exact distance between field marks?
The calculator now provides first and second planning marks using the published common shrink factor and ideal travel. Exact field marks can still depend on the bender, shoe radius, take-up, gain or deduct method, conduit springback, and manufacturer instructions.
What does theoretical shrink mean?
Theoretical shrink is the geometric reduction along the original run caused by the offset. The calculator uses true offset multiplied by the tangent of half the bend angle. Field results can vary with the bending method and equipment.
Review formulas and assumptions on the methodology page.