How to use the pipe offset travel calculator
- Choose a simple offset or a rolling offset.
- Enter the set, how far the pipe moves sideways, and for a rolling offset the roll, how far it moves up or down.
- Choose the fitting angle.
- Open More options to enter the take-out of one fitting, then read the travel and the pipe to cut.
Formula
true offset = square root of (set^2 + roll^2)
travel = true offset / sin(angle)
run gained = true offset / tan(angle)
pipe to cut = travel - 2 x take-out
A simple offset has no roll, so the true offset is the set. Travel is the center to center length between the two fittings.
A 10 inch offset with 45 degree fittings
The travel is 10 / sin(45 degrees) = 14.142 inches, and the pipe gains 10 inches of run. With no take-out the pipe to cut is also 14.142 inches.
With a 10 inch set and a 6 inch roll the true offset is 11.662 inches. At 45 degrees the travel is 16.492 inches, and with a take-out of 1.25 inches at each fitting the pipe to cut is 13.992 inches. An 8 inch set with a 15 inch roll has a true offset of 17 inches, so at 22.5 degrees the travel is 44.423 inches.
What a rolling offset is
A rolling offset moves the pipe sideways and up or down at once, for example to go around a beam and a duct together. The pipe travels along the diagonal of a box, so its true offset is the diagonal of the set and the roll. The fittings then turn the pipe by the chosen angle across that true offset.
The travel formula is the same as a simple offset once you replace the set with the true offset. Fittings must be rotated in the right plane, which is the hard part on the job and is outside this page.
Take-out and the cut length
Fittings have a length from their center to the bottom of the socket, and the pipe goes part of the way in. The distance the fitting takes up, less the engagement of the pipe, is the take-out. Subtract it at both ends to get the cut length. Use the figures in the data for your fitting, or leave it at 0 for a center to center length.
Related tools
The same geometry shapes conduit bends in the Conduit Offset Bend Calculator. Find what a pipe holds with the Pipe Volume Calculator, and solve other right triangles with the Triangle Calculator.
Assumptions and limits
- Both fittings have the angle you choose, and the pipe between them is straight.
- Set and roll are measured center to center.
- Take-out is the same for both fittings and for both ends of the cut pipe.
- Pipe expansion, hangers and fittings that are not exactly the stated angle are not included.
Frequently asked questions
How do I find the length of pipe in an offset?
Divide the offset by the sine of the fitting angle. A 10 inch offset with 45 degree fittings has a travel of 14.142 inches between the fitting centers.
What is a rolling offset?
It is an offset with both a sideways set and an up or down roll. Its true offset is the square root of the set squared plus the roll squared.
What is the multiplier for a 45 degree offset?
It is 1.414, which is one divided by the sine of 45 degrees. Multiply the offset by it to get the travel.
How do I allow for the fittings?
Subtract the take-out of each fitting from the travel. Enter it under More options. With 1.25 inches at each end the pipe in the rolling example is cut at 13.992 inches.