Offset Bend Calculator

Offset Bend Calculator results show the distance between bend marks, the shrink and where both marks go on the conduit. Enter the bend angle, offset depth and obstruction distance.

How the Offset Bend Calculator Lays Out Marks

An offset moves a conduit run sideways to clear an obstruction or to meet a box. Greenlee's hand bender manual describes it as two equal bends in opposite directions. The run comes out parallel to where it started, shifted by the offset depth.

Three numbers lay it out. The Offset Bend Calculator gives the distance between the two bend marks, the shrink, and the position of each mark from the end of the conduit. To calculate an offset bend by hand, multiply the offset depth by the multiplier for the bend angle.

$$D=H\times \frac{1}{\sin (\theta )}$$

D is the distance between marks, H is the offset depth and the angle is the bend at each mark. A 4 in offset with 30° bends needs 8 in between marks. With the obstruction 36 in away, the marks go at 37 in and 29 in from the same end.

The result box then reads Mark, Bend, Flip, Bend. Bend 30° at the first mark, roll the conduit 180° and bend 30° at the second. An offset that has to come back to the original line is a saddle, which the Saddle Bend Calculator lays out.

Offset Multipliers and Shrink by Angle

The multiplier is the cosecant of the bend angle. Bender makers round it for field use. The Bender Chart method uses the Offset Table from Greenlee's Site-Rite hand bender manual, which Greenlee says applies to any size of conduit.

The hand bender table has five angles, the same ones marked on the bender. The 15° row comes from Greenlee's 884 and 885 hydraulic bender manual, since hand benders have no 15° mark. A 4 in offset at 15° needs 15 7/16 in between marks with 1/2 in of shrink. The multiplier for a 30° offset bend is exactly 2, because the sine of 30° is 0.5.

The multiplier for a 45° offset bend is 1.4 on the chart and 1.414 exactly. The 1.414 formula is the offset depth times the square root of 2. On a 10 in offset the chart gives 14 in between marks and Exact Trigonometry gives 14 1/8 in.

The gap is larger at the ends of the chart. A 4 in offset at 10° is 24 in by the chart and 23 1/16 in exactly. At 60° it is 4 13/16 in against 4 5/8 in. The second card in the Offset Bend Calculator shows the other method's spacing beside the one in use.

Shrink has an exact form too. Each inch of depth shortens the run by the tangent of half the bend angle, and the chart rounds that to a sixteenth. Exact Trigonometry uses this figure, so a 4 in offset at 30° shows 1 1/16 in of shrink in place of 1 in.

$$S=H\times \tan \left(\frac{\theta }{2}\right)$$

Marks for 1 to 6 Inch Offsets

These are the distances between bend marks by the Greenlee chart, rounded to the nearest 1/16 in. To bend a 2 inch offset at 30°, put the marks 4 in apart. A 3 inch offset at 45° needs 4 3/16 in, and a 4 inch offset at 22.5° needs 10 3/8 in.

The This Offset at Every Bend Angle table in the Offset Bend Calculator builds the same comparison for any depth, with the shrink beside each spacing. Round Inches To switches the results between sixteenths, eighths, thirty-seconds and decimal inches.

Shrink When Working Toward an Obstruction

Bending an offset uses up length, so the conduit seems to shrink. If the first mark sits at the measured distance, the offset finishes short of the obstruction. The fix is to add the shrink to that distance before marking.

The default example in the Offset Bend Calculator has 1 in of shrink, which is 4 in of depth times 1/4 in. The first mark moves from 36 in to 37 in. The second mark is 8 in back toward the end, at 29 in. Both are measured from the same end, so one tape pull sets them.

Greenlee's manual works a 10 in offset at 45° with the obstruction 30 in away. It adds 3-3/4 in of shrink for a mark at 33-3/4 in and sets the marks 14 in apart. The Offset Bend Calculator returns 33 3/4 in for the first mark, 19 3/4 in for the second and 14 in between them.

When the obstruction is close to the end, the second mark can land past it. The fourth card then reads Obstruction Too Close to the End. A steeper angle shortens the spacing, or the bend can start from a longer piece.

Choosing an Angle That Fits the Space

Greenlee names two things to weigh. A steeper bend angle needs more pulling force on the wire, and a shallower one needs more space. The run along the surface is the space the offset takes up, and it is the offset depth divided by the tangent of the angle.

A 4 in offset at 30° takes 6 15/16 in of run. Enter 12 in under Space Available and the fourth card in the Offset Bend Calculator reads Offset Fits the Space with 5 1/16 in left over. It also names 22.5° as the shallowest hand bender angle that still fits. With only 6 in available, the card turns red and the alert says a 45° offset fits.

Every bend also counts toward a code limit. NEC 358.26 allows no more than 360° of bends in EMT between pull points. A 30° offset uses 60° of that and a 45° offset uses 90°. A run that goes over needs a pull point, which the Pull Box Sizing Calculator sizes.

Parallel Conduit Offsets

Side-by-side conduits bent with identical marks do not stay evenly spaced through the offset. Each one needs its marks shifted along the pipe. The shift is the center spacing times the tangent of half the bend angle.

For conduits 2 in apart on center, the shift is 9/16 in at 30° and 13/16 in at 45°. The second card of this conduit offset bend calculator shows it as Mark Shift per Parallel Conduit. An electrician on the Mike Holt forum asked whether to move one mark or both. Both marks move by the same amount, so the distance between them stays the same.

Metric and Pipe Offset Bend Calculator

The geometry is the same for any round material, so the same numbers serve for pipe and for steel conduit such as EMT, IMC and rigid. For pipe joined with 45° fittings, the travel between fitting centers is the offset times 1.414. Pick Exact Trigonometry for that, since the chart values are rounded for benders.

A rolling offset shifts the pipe sideways and up at once. Find the true offset first, which is the square root of the two offsets squared and added. A 3 in rise with a 4 in sideways shift is a true offset of 5 in. Enter 5 in at 45° in the Offset Bend Calculator and the exact spacing is 7 1/16 in.

For a metric layout, switch the Offset Depth unit to millimeters or centimeters. A 100 mm offset at 30° gives 200 mm between marks and 25 mm of shrink. The third card always shows the same three layout numbers in the other system, so the default example also reads 203 mm, 940 mm and 737 mm.

45 Degree Offset Calculator Steps

How do you bend a 45 degree offset?

Measure the offset depth and multiply it by 1.4 for the distance between marks. Add 3/8 in of shrink for each inch of depth to the distance to the obstruction, and put the first mark there. Put the second mark back toward the end by the spacing.

For a 5 in offset that is 7 in between marks and 1 7/8 in of shrink. Line up the first mark with the arrow on the bender and bend to the 45° mark. Roll the conduit 180°, line up the second mark and bend 45° again. Keep both bends in the same plane.

How do you bend a 30 degree offset?

The steps are the same with easier numbers. The distance between marks is twice the offset depth, and the shrink is 1/4 in per inch. A 6 in offset needs 12 in between marks and 1 1/2 in of shrink, which matches the worked example in Greenlee's hydraulic bender manual.

A 22.5 degree offset uses a multiplier of 2.6 and 3/16 in of shrink per inch. It takes more run than 30° but pulls easier. The 30° bend is the common choice because the math is simple and the pull stays moderate.

How many degrees is an offset bend?

Any angle works as long as both bends match. Hand benders are marked at 10°, 22.5°, 30°, 45° and 60°, so those are the usual choices. Shallow 10° bends suit small offsets into a box, and 45° or 60° bends are for tight spaces.

A 45 bend is a single bend of 45°, and a 45° offset is two of them. The Offset Bend Calculator accepts any angle from 1° to 75°. Angles off the chart are worked by exact trigonometry.