Enter the rise and the roll. Get the true offset, the center-to-center travel of the offset pipe, the set-back, and the roll angle, for a 45, 22.5, 60 degree or custom fitting. A simple offset calculator is below. Free, no account, runs in your browser and works offline once loaded.
An Android app with ASME B16.9 fitting take-outs and cut lengths is coming.
| Term | Meaning |
|---|---|
| Rise | How far the pipe moves vertically. |
| Roll | How far the pipe moves sideways. Rise and roll are at right angles to each other. |
| True offset | The straight-line distance between the two pipe centerlines, square root of rise squared plus roll squared. This is the number you use as the "set" of an ordinary offset. |
| Travel | Center-to-center length of the diagonal pipe between the two fittings. True offset divided by sin of the fitting angle. |
| Set-back | How far along the main line the offset takes. True offset divided by tan of the fitting angle. |
| Roll angle | The tilt of the offset plane, measured from the rise direction, atan of roll over rise. Rise 6 and roll 8 gives 53.13 degrees. |
Subtract the take-out of each fitting from the travel to get the cut length of the diagonal pipe. Take-out depends on the fitting type, pipe size and weld gap, so look it up for your fitting. Set the two fittings so the plane through both pipes is tilted by the roll angle from vertical, then check the first one with a level before you tack.
Fitting factors for a simple offset, travel and set-back per 1 unit of offset: 60 degrees 1.1547 and 0.5774, 45 degrees 1.4142 and 1.0, 30 degrees 2.0 and 1.7321, 22.5 degrees 2.6131 and 2.4142, 11.25 degrees 5.1258 and 5.0273.
Worked check: rise 16, roll 12, 45 degree fittings. True offset 20, travel 28.28. The 12-16-20 triangle is the 3-4-5 triangle scaled up, so you can verify it by hand.
A simple offset moves the pipe in one plane. A rolling offset moves it in two directions at once, up and sideways. Once you reduce rise and roll to one true offset, the rest of the math is the same as a simple offset in a tilted plane.
No. Any fitting angle works if both fittings match. 45 is the most common because the travel is 1.4142 times the offset. Pick Custom for anything else.
No. Results are center-to-center, so you can use them with any fitting type. Subtract the take-out for your fitting and weld gap yourself.
No. The calculation runs in your browser and nothing is uploaded or stored.
This is a layout aid. Check critical work against your own drawings and company standards.