Rolling offset mark worksheet
Parallel Offset Spacing Calculator
Calculate mark spacing and second mark location after the true offset and bend angle are known.
Calculate Parallel Offset Spacing
Enter true offset, bend angle, and first mark to calculate spacing and second mark for a rolling or parallel offset.
Result
Bend spacing
14.422 in
Distance between marks based on the true offset.
Second mark
38.422 in
Result notes. Keep inputs, assumptions, and result together before using this value in project records.
Keep the entered values, assumptions, and result together when adding this calculation to job notes or submittal records. Final installation choices should align with the applicable code edition, equipment listing, manufacturer instructions, local amendments, and AHJ requirements.
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Related charts
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Use offset multiplier chart: 15 deg = 3.9, 22.5 deg = 2.6, 30 deg = 2.0 and 45 deg = 1.414; a 4 in offset at 30 deg marks 8 in.
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Formula and field context
Calculate mark spacing and second mark location after the true offset and bend angle are known.
Formula context
Parallel Roll Offset Chart
A rolling offset moves conduit in two directions at once, so spacing is based on the diagonal true offset rather than only the rise or side movement. The calculator combines horizontal and vertical offsets, applies the selected bend multiplier, and reports the roll angle needed to rotate the bend plane. Use this chart to keep rotation direction, mark spacing, and shrink tied together before bending.
Formula
True offset = sqrt(horizontal offset^2 + vertical offset^2). Roll angle = atan2(horizontal offset, vertical offset). Mark spacing = true offset x multiplier.Variables to keep with the result
- Horizontal offset is the side-to-side movement of the conduit centerline.
- Vertical offset is the rise or drop of the conduit centerline.
- True offset is the diagonal movement used for mark spacing and shrink.
- Roll angle is the rotation of the bend plane from vertical toward the horizontal offset.
Formula and variables
Parallel offset spacing uses the true offset and the selected bend multiplier. The formula is spacing = true offset x multiplier. If the first mark is known, second mark = first mark + spacing. True offset may come from a rolling offset geometry calculation or from a field measurement. Bend angle controls the multiplier, and both marks must be measured from the same reference end.
Field example
A rolling offset with 6 in horizontal movement and 4 in vertical movement has a true offset of 7.211 in. With 30 degree bends, the multiplier is 2.0, so spacing = 7.211 x 2.0 = 14.422 in. If the first mark is 24 in from the conduit end, the second mark is 24 + 14.422 = 38.422 in from the same end.
Assumptions and layout limits
This worksheet starts after the true offset is known. It does not calculate roll angle, rotation direction, shrink, support clearance, or whether the conduit should roll left or right. Use it for the mark-spacing step only. Use the rolling offset travel tool when horizontal and vertical movements still need to be combined, and use the full calculator when all layout values must be reviewed together.
Common mistakes
Common mistakes include entering only the vertical rise instead of true offset, measuring the second mark from the first mark rather than from the same end, using the wrong bend multiplier, and forgetting to label roll direction on the conduit. Keep true offset, angle, multiplier, first mark, second mark, and bend-plane direction in the field note.