Offset Bend Calculator

What the Calculator Solves

An offset bend moves a conduit run laterally by a fixed distance — the offset rise — to clear an obstruction, step around a beam, or align with a panel or box, then return the conduit to its original plane of travel. The offset is formed by two equal bends of the same angle, one bent in each direction. Laying this out correctly requires knowing where to place the second bend mark relative to the first mark, how much conduit length the bends consume (travel), and how much total conduit length is lost to the bending process (shrink). The Offset Bend Calculator produces all three figures from three field inputs: offset rise, bend angle, and the first mark distance from the conduit end.

Inputs and Their Role

Offset rise is the perpendicular distance between the two straight conduit runs after the offset is complete — the actual clearance the offset must achieve, entered in inches. If the obstruction requires additional working clearance beyond the physical dimension, that clearance must be added into the rise value manually before entry; the calculator does not add clearance on its own.

Bend angle is the angle of each individual bend, not the combined angle between the two straight runs. This is a critical distinction on the bender shoe: a 30° offset means each bend is set at 30° on the bender’s angle scale, not that the two runs diverge by 30°. Field marks commonly used are 10°, 22.5°, 30°, and 45°. Any other angle should be checked against the degree markings stamped on the actual bender shoe, since not all benders carry marks beyond the standard set.

First mark from conduit end is the reference distance from the cut end of the conduit to where the first bend will start. This anchors the entire layout; every other output is measured relative to it.

Formula and Calculation Steps

The calculator applies standard conduit-bending trigonometry:

Offset multiplier = 1 / sin(bend angle)

Travel between marks = Offset rise × Offset multiplier

Second bend mark = First bend mark + Travel between marks

Estimated shrink = Offset rise × tan(bend angle / 2)

The multiplier converts the required rise into the actual center-to-center distance the two bends must be spaced apart along the conduit — this distance is always longer than the rise itself because the conduit travels diagonally between the bends. Shrink is the length the conduit effectively “gives up” from its overall run because the diagonal path between bends is longer than the straight-line distance it replaces; if shrink isn’t accounted for, the finished conduit ends up short of its intended termination point.

Worked Example

Field	Value
Offset rise	4 in
Bend angle	30 deg
First mark from conduit end	24 in
Offset multiplier	2×
Travel between marks	8 in
Second bend mark	32 in
Estimated shrink	1.0718 in

With a 4 in rise at 30°, the multiplier is 1/sin(30°) = 2. Travel is 4 in × 2 = 8 in, so the second bend starts 8 in past the first. Since the first mark is set at 24 in from the conduit end, the second mark falls at 32 in. Shrink is 4 in × tan(15°) = 4 in × 0.2679 ≈ 1.0718 in — meaning the overall conduit run effectively shortens by roughly 1.07 in once both bends are made, and this length should be added back at the far end if the conduit must land on an exact termination point (box, fitting, or panel knockout).

Practical Use in Layout Work

The second bend mark and travel values are what get transferred directly to the conduit with a marker before bending — they tell the installer exactly where to align the arrow or notch on the bender shoe for the second bend. The estimated shrink value is used to adjust the starting measurement on longer runs where the offset sits between two fixed points, so the final conductor or raceway length lands where designed rather than short. On multi-offset runs (saddle bends or multiple offsets in one stick of conduit), shrink accumulates and must be tracked per offset, not just once for the whole run.

Field Verification

The calculator performs pure trigonometric arithmetic on ideal geometry and does not account for bender-specific take-up, the small length consumed at the bend point that varies by conduit size, wall thickness, and bender model. Manufacturers publish take-up figures separately, and these should be checked against the bender in use before cutting conduit to final length. The angle used must match the shoe’s actual degree mark rather than an assumed value, since bender scales are not universally identical across manufacturers. Bend angle, rise, and mark placement affect only conduit geometry and layout — they carry no bearing on conductor ampacity, raceway fill, or voltage drop, which remain separate calculations governed by the applicable NEC articles and verified against the AHJ‘s adopted code edition.