For a two-bend conduit offset, multiply the required offset depth by the angle multiplier to find the distance between bend marks. A 30-degree offset uses a multiplier of 2, so a 6-inch offset calls for 12 inches between marks. The table below separates manufacturer field constants from calculated (1/\sin(\theta)) values, because familiar constants—especially 6 at 10 degrees—are practical approximations rather than exact trigonometric values.
Offset Multiplier Table: 10 to 45 Degrees
| Angle of each bend | Manufacturer field multiplier | Calculated (1/\sin(\theta)), rounded | Spacing for a 6-inch offset using the field multiplier | Manufacturer shrink allowance per inch of offset depth |
|---|---|---|---|---|
| 10° | 6.0 | 5.7588 | 36.00 in. | 1/16 in. |
| 15° | 3.86 | 3.8637 | 23.16 in. | 1/8 in. |
| 22.5° | 2.6 | 2.6131 | 15.60 in. | 3/16 in. |
| 30° | 2.0 | 2.0000 | 12.00 in. | 1/4 in. |
| 45° | 1.4 | 1.4142 | 8.40 in. | 3/8 in. |
The field multipliers and shrink allowances come from the Greenlee 880 instruction manual, IM 689 Rev. 9, dated March 2019, pages 8–9. The trigonometric column and 6-inch spacing column are calculated comparisons, not additional manufacturer specifications. These reference values were checked for this 2026 article; the underlying manual remains a 2019 document.
Use this table for an ordinary offset with two equal bends in opposite directions, leaving the incoming and outgoing conduit sections parallel. The multiplier is dimensionless: offset depth in inches produces spacing in inches, and offset depth in millimeters produces spacing in millimeters. The inch-based shrink column expresses inches of allowance per inch of offset depth.
These are layout references, not allowable bend-radius limits or proof that a particular offset will fit your bender. The Greenlee manual includes separate conduit-size and spacing restrictions for its equipment; use the instructions for your actual bender, shoe, conduit type, and trade size.
Where the Offset Multiplier Comes From
The basic offset model forms a right triangle. Offset depth is the perpendicular distance between the two parallel conduit centerlines, and the diagonal side represents the idealized travel between bend locations.
Let:
- (h) = required offset depth.
- (\theta) = angle of each bend relative to the original run.
- (L) = idealized distance between bend locations.
- (M) = offset multiplier.
Then:
[
\sin(\theta)=\frac{h}{L}
]
Rearranging gives:
[
L=\frac{h}{\sin(\theta)}=hM
]
[
M=\frac{1}{\sin(\theta)}
]
This explains the angle comparison in the table: smaller angles require more distance to achieve the same offset depth. Greenlee’s layout method uses the same height-times-multiplier relationship to calculate center-to-center bend distance.
Why the 30-Degree Multiplier Is Exactly 2
At 30 degrees:
[
\sin(30^\circ)=0.5
]
Therefore:
[
M=\frac{1}{0.5}=2
]
The 30-degree multiplier is exact within this triangle model, rather than merely a convenient rounded constant. That makes 30-degree offsets easy to calculate by hand: double the required offset depth to obtain the nominal bend-mark spacing. Both Greenlee’s manual and Klein Tools’ offset guide show 12 inches between bends for a 6-inch, 30-degree offset.
The model does not represent the complete curved centerline of a real conduit bend. Actual bends have a radius, and finished dimensions also depend on the bender’s reference marks and springback. Treat the calculation as a layout starting point, then verify the finished offset.
Choosing an Angle and Calculation Method
For the same offset depth, a shallow angle needs more room along the run, while a steeper angle brings the bends closer together. The manufacturer shrink allowance also increases across the angles shown, so choosing a steeper angle changes both spacing and longitudinal layout.
| Layout priority | Angle or method to consider | What to check |
|---|---|---|
| A shallow change in direction with ample room along the run | 10° or 15° | Longer spacing and available straight conduit |
| Simple hand calculation | 30° | Offset depth × 2; verify clearance and bender limits |
| Less distance between bends for the same offset depth | 45° | Larger shrink allowance and minimum feasible spacing |
| Reproducing a manufacturer’s field layout | Manufacturer multiplier | Use that manual’s marking and shrink conventions |
| Checking the underlying geometry | (1/\sin(\theta)) | Use degree mode and recognize the idealized model |
The angle comparisons follow the manufacturer table; equipment suitability must be checked separately.
Do not silently mix field constants with calculated trigonometric values. For a hypothetical 6-inch offset at 10 degrees, the field constant gives (6\times6=36) inches, while the triangle calculation gives (6/\sin(10^\circ)\approx34.55) inches. The roughly 1.45-inch difference is why the method should be stated explicitly rather than presenting 6.0 as the exact reciprocal of the sine.
Worked Example: A 6-Inch Offset at 30 Degrees
This hypothetical layout example assumes two equal 30-degree bends in one plane. The required centerline offset is 6 inches, and the selected bender and conduit can accommodate the proposed layout.
| Input or assumption | Value |
|---|---|
| Required offset depth, (h) | 6 in. |
| Angle of each bend, (\theta) | 30° |
| Multiplier, (M) | 2.0 |
| Manufacturer shrink allowance | 1/4 in. per inch of offset depth |
| Layout type | Two equal, opposite bends; parallel end sections |
The multiplier and shrink allowance match the manufacturer references.
- Confirm the required offset depth. Measure the centerline displacement needed for the route, allowing for the actual obstruction and clearance—not just its height.
2. Calculate the bend spacing:
[
L=hM=6\text{ in.}\times2=12\text{ in.}
]
3. Calculate the manufacturer’s shrink allowance when the layout requires it:
[
S=6\text{ in.}\times\frac{1}{4}=1.5\text{ in.}
]
- Locate the marks using the actual bender’s instructions. The 12-inch result establishes their separation; it does not establish their absolute positions along the conduit.
- Verify the finished offset depth, parallel end sections, and obstruction clearance before treating the layout as complete.
The resulting nominal spacing is 12 inches, with a 1.5-inch field shrink allowance. Greenlee’s manual gives this same example. Its toward-obstruction layout places the second mark 1.5 inches beyond the obstruction reference and measures back 12 inches to locate the other mark.
For another arithmetic check, use the conduit-bending calculator with the same offset depth and bend angle. When comparing results, identify whether the calculation uses field constants or trigonometric values; agreement on spacing does not validate the entire installation.
Shrink and Marking Conventions
Shrink is the longitudinal allowance associated with forming an offset; it is not the distance between bend marks. Greenlee treats it as an adjustment needed when approaching an obstruction, while Klein’s guide also includes it when locating the offset marks.
A spacing multiplier and a shrink allowance solve different layout problems. Also, “first bend” can describe the order of bending rather than the mark nearest the conduit end. Follow the diagram and reference direction in your bender’s manual instead of transferring a marking sequence from another tool.
The listed shrink allowances are manufacturer field references. Keep them identified as such rather than presenting them as exact outputs of the sine formula. This distinction matters when an offset must meet a tightly located obstruction or termination.
Manufacturer References and Layout Limits
For the source table, consult the Greenlee 880 instruction manual, pages 8–9. Its equipment-specific spacing table also demonstrates why a multiplier alone cannot determine whether a small offset is feasible for a given conduit size.
For a hand-bender comparison, consult the Klein Tools Conduit Bender and Angle Setter guide, Rev. 09/20 A. Its offset chart supplies rounded tape-measure dimensions, including 12-inch spacing and 1-1/2-inch shrink for the 6-inch, 30-degree example.
Neither this table nor a calculator replaces manufacturer instructions, applicable NEC requirements, the local authority having jurisdiction, or professional assessment of the route. A correct spacing calculation is not approval of bend radius, total bends, conduit condition, or installation compliance.
Offset Layout Checklist
Use this check before committing to the layout. It separates arithmetic errors from the equipment and fit checks that multiplication cannot resolve.
- Measure the required centerline offset, including necessary clearance.
- Use the same length unit throughout the calculation.
- Confirm that both bends use the intended equal angle.
- Set the calculator to degrees, not radians.
- Identify whether the multiplier is a field constant or a trigonometric value.
- Keep bend spacing separate from shrink allowance.
- Follow the correct bender reference mark and layout direction.
- Check conduit type, trade size, shoe compatibility, and minimum feasible spacing.
- Verify finished offset depth, parallel alignment, clearance, and conduit condition.