A rolling offset changes pipe centerline position in two perpendicular directions at once. The local geometry is straightforward: true offset is the hypotenuse formed by the entered set and roll, centerline travel is true offset divided by the sine of the nominal fitting angle, and advance is true offset divided by the tangent of that angle.
Those numbers are useful for screening and learning, but they are not a final spool drawing or pipe cut length. Production layout still depends on actual fitting takeout, joining allowance, weld gap, shrinkage, manufacturer dimensions, project isometrics, adopted code, inspection, permits, and qualified review.
Centerline Geometry Only
Use centerline set for the horizontal movement and centerline roll for the vertical movement. The right-triangle screen is true offset = √(set² + roll²). For a nominal fitting angle, centerline travel = true offset / sin(angle), and advance = true offset / tan(angle).
The orientation-angle prompt is atan2(roll, set), measured from the entered set direction toward the entered roll direction. A shop or field mark may use a different reference line depending on pipe position, viewing direction, handedness, and the physical route.
Set = 12 in, Roll = 6 in, Angle = 45°
True offset = 13.416 in
Centerline travel = 18.974 in
Advance = 13.416 in
Orientation prompt = 26.565°
This validates arithmetic only, not final cut length, takeout, fit-up, code, or safety.
Pipe Rolling Offset Calculator
Calculate pipe rolling offset travel length for any fitting angle. Enter set and roll to get travel, advance, and cut length. 45, 22.5, 30, and 60 degree support.
Why Travel Is Not Cut Length
Centerline travel is measured between fitting center points. The straight pipe piece between fittings is shorter or otherwise adjusted depending on actual fitting takeout, socket or thread engagement, groove allowance, weld root gap, bevel, weld shrinkage, gasket thickness, flange face-to-face dimensions, and field-fit allowance.
Use actual manufacturer dimensions, project drawings, and the joining method before cutting. A geometry screen cannot know whether the assembly is butt-welded, threaded, socket-welded, soldered, brazed, grooved, flanged, sanitary, lined, plastic, or field-fit.
Pipe Spool Take-Out Calculator
Calculate exact pipe cut lengths by subtracting fitting take-out dimensions. Supports 90, 45, tee, and weld fittings with gap allowance.
Source Boundaries to Keep Visible
ASME B16.9 is a source pointer for factory-made wrought buttwelding fittings, but the local rolling-offset screen does not reproduce B16.9 tables, pressure ratings, or tolerances. ASME B31.1 and B31.3 source pointers identify piping-code boundaries, not automatic code compliance.
PFI fabrication standards, welding-code requirements, OSHA hot-work rules, owner specifications, permits, AHJ review, and inspection criteria remain outside the app. Treat these as unresolved source gaps until the current project sources and qualified reviewers close them.
ASME-B16-9-SOURCE
ASME-B31-1-2024-SOURCE
ASME-B31-3-2024-SOURCE
PFI-STANDARDS-PRODUCTS-2026
AWS-D1-1-2025-STRUCTURAL-WELDING-CODE-SOURCE
OSHA-1910-252-WELDING-CUTTING-BRAZING-2026
OSHA-1926-350-GAS-WELDING-CUTTING-2026
NIST-SP811-B8
Field and Shop Review Items
Before layout, confirm that set and roll are measured from the same centerline reference and that the physical reference line is marked. Check actual fitting dimensions, pipe OD, wall, ovality, route constraints, slope, supports, clashes, and whether the offset changes pressure, flow, thermal movement, or support loads.
Before any hot work or pressure-piping task, resolve LOTO, depressurization, pressure isolation, gas freeing, confined-space controls, cylinder and torch safety, ventilation, fire watch, PPE, WPS/PQR/WPQ, inspection, and pressure testing. The app is not a safe-work permit or work authorization.