Trade ToolkitTools › Plumbing
Pipe offset calculator
Travel, run and cut for any fitting angle.
Open the Pipe Offset toolFree. Runs in your browser, no account, and keeps working offline.
What it does
Enter how far the pipe needs to move, center to center, and the angle of the fittings (45°, 22 1/2°, 60° or any other). The calculator gives the travel between the fittings, how far the offset advances along the pipe, and the multiplier from the plumber's chart.
Subtract a fitting allowance at each end and it gives the length of pipe to cut. For PVC DWV 45s and 22 1/2s the typical center-to-socket figures are filled in; makers differ a little, so measure the fittings in hand.
For a rolling offset, enter both the rise and the spread; it works out the true offset and the rest follows.
Worked example
A 12″ offset, center to center, with two 2″ PVC DWV 45° fittings (about 1 1/2″ each from center to the bottom of the socket).
- Travel (center to center)
- 17″
- Run (advance along the pipe)
- 12″
- Multiplier
- 1.414
- Pipe to cut
- 14″
Fitting allowances vary by maker; measure the fittings in hand.
Questions
How do I calculate a 45° pipe offset?
Multiply the offset by 1.414 to get the travel, center to center. Subtract the fitting allowance at each end to get the pipe to cut.
What is a rolling offset?
An offset that moves up and sideways at once. The true offset is the diagonal of the rise and the spread; use it like a simple offset.
What is the fitting allowance?
The distance from where a fitting's center lines cross to the bottom of its socket. See the fitting allowance chart for PVC DWV.