123 123Calculator

Rolling Offset Calculator

Find a pipe rolling offset's travel and run values using this rolling offset calculator.

Clear
Travel (pipe between fittings)21 3/16 in21.2132 in · 538.82 mm
True offset15 inthe diagonal across the vertical and the roll
Run15 inthe horizontal distance along the original line
Vertical offset12 in
Horizontal roll9 in
Roll angle53.13°how far round from horizontal to rotate the fitting
Fitting angle45°multiplier 1 ÷ sin θ = 1.41421
Travel multiplier1.41421multiply the true offset by this
Run multiplier1
Check: travel² − offset²15 inshould equal the run, and does
Remember the take-offdeduct it from the travelthe travel is centre to centre — subtract each fitting’s take-off to get the pipe length to cut

The formula

true offset = √(vertical² + roll²); travel = offset ÷ sin θ

Two offsets at once

A rolling offset moves a pipe both sideways and up or down in a single pair of fittings. The trick is that the two offsets combine as a right triangle: the true offset is the diagonal, √(vertical² + roll²), and from there it is an ordinary offset calculation.

For 45° fittings the travel is the true offset times √2, about 1.414, and the run equals the true offset exactly. That is why 45s are the default — the arithmetic is easy and the flow characteristics are good.

The travel is measured centre to centre of the fittings. The pipe you actually cut is shorter by each fitting’s take-off, which depends on its size and pattern.