Rolling Offset Calculator — Pipe & Conduit Bending
When a pipe or conduit must clear an obstacle by moving both up (or down) and sideways at the same time, the result is a rolling offset. Enter the vertical rise, the horizontal spread, and the fitting bend angle to get the true (diagonal) offset, the travel length between the two fittings, and the advance along the pipe run.
mm
mm
Bend angle
Diagonal distance = √(rise² + spread²)
- 1
Rise squared
300² = 90,000 - 2
Spread squared
400² = 160,000 - 3
Sum of squares
90,000 + 160,000 = 250,000 - 4
True offset
√250,000 = 500Pythagorean diagonal bridging the vertical rise and horizontal spread.
How does this calculator work?
Rolling offset combines a vertical rise and a horizontal spread into a diagonal true offset = √(rise² + spread²). For a pair of 45° bends, travel = true_offset × 1.414 and run = true_offset. Use this to find the pipe cut length between the two offset fittings when the pipe must clear an obstacle in two directions at once.
Formula
How this is calculated
A standard offset bends in one plane; a rolling offset bends in two planes simultaneously. The true (rolling) offset is the straight-line diagonal distance the pipe must bridge, found by the Pythagorean theorem: √(rise² + spread²), where rise is the vertical change and spread is the side-to-side change. This diagonal lies in the plane that is tilted relative to both the horizontal and vertical planes — hence the term "rolling".
Once the true offset is known, it behaves exactly like a standard in-plane offset. For a pair of equal-angle fittings at angle θ (typically 45°), the travel (pipe length between the two fitting sockets) equals true_offset / sin(θ), and the advance (distance gained along the overall pipe run direction) equals true_offset / tan(θ).
For 45° bends — by far the most common choice — the formulas simplify to: travel = true_offset × √2 ≈ 1.414 × true_offset, and run = true_offset × 1.000 (the advance equals the true offset). These are the numbers printed on most plumber offset cheat-sheets. Remember to add the fitting makeup (socket engagement) to the pipe cut length for your actual cut measurement.
Frequently asked questions
A regular (simple) offset moves the pipe in a single plane — either left/right or up/down. A rolling offset does both simultaneously: the pipe must change elevation and move sideways at the same time, so the bends are rotated ("rolled") relative to vertical. The geometry is the same as a right triangle with sides = rise and spread and hypotenuse = true offset.
45° bends are the most common because the travel formula is simple (× 1.414) and fittings are widely available. 22.5° and 30° offsets create a shallower, more gradual change and can be preferred where headroom is limited, but the travel is longer. 60° bends give a steeper offset in less travel, though fittings are less common in some systems.
The travel figure gives the centreline-to-centreline dimension between the two fittings. Subtract the makeup depth (socket engagement depth) of each fitting to find the actual cut length. Makeup depth varies by fitting material, size and manufacturer — check the fitting datasheet or measure your test fitting.
Also known as
TG we-Calculate Editorial Team. (2026). Rolling Offset Calculator — Pipe & Conduit Bending [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/rolling-offset-calculator
TG we-Calculate Editorial Team. "Rolling Offset Calculator — Pipe & Conduit Bending." TG we-Calculate. 2026. https://we-calculate.com/calculator/rolling-offset-calculator.
TG we-Calculate Editorial Team, "Rolling Offset Calculator — Pipe & Conduit Bending," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/rolling-offset-calculator
@misc{wecalculate_rolling_offset_calculator, title = {Rolling Offset Calculator — Pipe & Conduit Bending}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/rolling-offset-calculator}}, year = {2026}, note = {TG we-Calculate} }
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