What are travel, offset and run?

In a simple offset, the offset (or set) is how far the pipe shifts sideways, the travel is the diagonal pipe length between the two fittings, and the run is how far the pipe advances along its original direction. Together they form a right triangle with the fitting angle.

How is travel calculated from the offset?

Travel equals offset divided by the sine of the fitting angle, which is the same as offset times the cosecant of the angle. For 45 degrees the cosecant is 1.414, so a 10 inch offset needs a 14.14 inch travel between fitting centers.

Why do plumbers memorize constants like 1.414?

Multiplying the offset by a fixed constant for each angle is faster than reaching for a calculator on the job. 1.414 for 45 degrees, 2.613 for 22.5 degrees and 1.155 for 60 degrees are the classic travel constants pipefitters keep on hand.

Do I cut the pipe to the travel length?

Not exactly. Travel is the center-to-center distance between fittings. You must subtract the fitting take-out (the lay length each fitting consumes) from both ends to get the actual pipe cut length, which is why this tool lets you enter a fitting allowance.

What is a rolling offset?

A rolling offset shifts the pipe both horizontally and vertically at once. You first combine the horizontal and vertical offsets into a single true offset with the Pythagorean theorem, then apply the same travel constant. This tool covers the simple in-plane offset; compute the true offset first for rolling work.

Pipe Offset / Travel Calculator (Plumbing Isometric)

When a pipe has to jog around an obstruction, the plumber sets two fittings and runs a diagonal between them. This calculator solves that offset triangle for any standard fitting angle, giving the travel (diagonal cut length), the run, and the net pipe length after subtracting fitting take-out.

How it works

The offset, travel and run form a right triangle where the fitting angle is measured from the original pipe line:

travel = offset / sin(angle)   = offset × cosecant(angle)
run    = offset / tan(angle)   = offset × cotangent(angle)
cut    = travel − 2 × fitting take-out

The classic memorized constants fall straight out of this: cosecant of 45° is 1.414, of 22.5° is 2.613, of 60° is 1.155, and of 30° is 2.000. Multiply your offset by the constant to get travel without trigonometry on the job.

Example and notes

To clear a 10-inch obstruction with 45° fittings, travel is 10 × 1.414 = 14.14 inches center to center, and the run is also 10 inches. If each fitting has a 1-inch take-out, the actual pipe cut is 14.14 − 2 = 12.14 inches. Smaller angles like 22.5° give a longer, gentler diagonal that drains better and adds less turbulence, while 60° fittings make a tight, abrupt offset in confined spaces. For a rolling offset, combine the horizontal and vertical shifts into one true offset first, then apply the constant.