Rolling Offset Calculator
Rolling offset calculator for pipefitters: enter roll, set, and fitting angle to get the true offset, travel (cut length), and run for angled pipe around obstructions.
Rolling Offset Calculator: Pipe Travel, Run, and True Offset
A rolling offset routes a pipe around an obstruction in two directions at once — sideways ("roll") and up or down ("set") — rather than the single-plane jog a simple offset makes. Because the bend is diagonal, the pipe travels further between fittings than either the roll or the set alone suggests. This calculator takes the roll, the set, and the fitting angle you plan to use, and returns the true offset, the travel (the length to mark and cut the pipe to), and the run.
How to use the rolling offset calculator
- Enter the roll — the horizontal offset the pipe must clear.
- Enter the set — the vertical offset the pipe must clear.
- Choose the fitting angle (22½°, 45°, 60°, 90°, or a custom angle) — the bend angle of the fittings you are using.
- Read off the true offset, travel, and run, plus the offset multiplier for that angle.
The rolling offset formula
The roll and set combine like the two legs of a right triangle into a true offset: c = sqrt(roll² + set²). Travel — the length to mark and cut on the pipe — is travel = c / sin(theta), and run is run = c / tan(theta), where theta is the fitting angle.
Example: a 1 ft roll and a 1 ft set with 45° fittings give a true offset of sqrt(1² + 1²) = 1.414 ft. Travel = 1.414 / sin(45°) = 1.414 / 0.7071 ≈ 2.0 ft, and run = 1.414 / tan(45°) = 1.414 ft. The travel-to-offset ratio (2.0 / 1.414 ≈ 1.414) is the standard 45° offset multiplier pipefitters use as a shortcut.
Tips
Always mark and cut to the travel length, not the true offset or the run — travel is the actual diagonal distance between the two fittings.
A 45° rolling offset is the most common in the field because its multiplier (1.414) is easy to remember; 60° gives a shorter travel in tighter spaces at the cost of a sharper bend.
In the UK, a plumber typically charges about £130-£450 to cut and fit a rolling offset around an obstruction, depending on pipe size and access.
