Pipe offset calculator: 45°, 30° & 22.5° travel math
Route a pipe around an obstacle without guessing. A pipe offset calculator turns your offset distance and fitting angle into the exact travel and run — and PlumbCalc Pro does it free.
A pipe offset is the jog you put in a run to step it over, under, or around something — a beam, a duct, another pipe — and then continue parallel to the original line. The pipe offset calculator answers the two numbers you actually need on the job: the travel (the diagonal length of pipe between the two fittings) and the run (how far the offset carries you along the original direction). Get them right and the pipe drops straight into place; get them wrong and you're back at the saw. Results here are estimates for guidance, not a substitute for local code.
Open the PlumbCalc Pro calculators to run your numbers instantly.
Pipe offset multipliers (the constants)
Every simple offset is just your offset distance multiplied by a constant that depends on the fitting angle. Keep these four in your head or on your phone:
| Fitting angle | Travel = offset × | Run = offset × |
|---|---|---|
| 45° | 1.414 | 1.000 |
| 30° | 2.000 | 1.732 |
| 22.5° | 2.613 | 2.414 |
| 60° | 1.155 | 0.577 |
The 45° fitting is the workhorse because the run equals the offset exactly (multiplier 1.000), which makes layout easy. Shallower angles like 22.5° need much more travel and run, but they flow better and are gentler on drainage.
How to calculate a pipe offset
1. Measure the offset — the center-to-center distance between the two parallel runs.
2. Pick your fitting angle (45°, 30°, 22.5°, 60°).
3. Travel = offset × the travel constant. This is the diagonal pipe length between the fittings.
4. Run = offset × the run constant. This is how far the offset moves you down the line.
Worked example. You need to jump a 10-inch offset with 45° fittings. Travel = 10 × 1.414 = 14.14″ of pipe between the fittings; run = 10 × 1.000 = 10″. Cut your 14⅛″ piece, and you'll land exactly 10″ over and parallel. These constants come straight from the trig of a right triangle — the same relationships tabulated in references like the Engineering ToolBox.
Remember to subtract fitting take-off
The travel number is the center-to-center length. Before you cut, subtract the make-up (take-off) of each fitting so the pipe seats to the right depth in the sockets. That's the one step that trips people up — the math is right, but the cut is long if you forget the fittings.
More PlumbCalc Pro calculators
Offsets are one piece of the job. Size the pipe itself with the pipe diameter calculator and pipe sizing calculator, size gas with the gas line sizing calculator, and check flow and capacity with the water flow rate calculator and pipe volume calculator. Save any job to Projects.
Run your offset in seconds
PlumbCalc Pro does the travel and run math for you — free, right in your browser.
Open PlumbCalc Pro ▶ Subscribe on YouTubePipe offset calculator — frequently asked questions
How do you calculate a pipe offset?
Multiply the offset by the fitting's travel constant for the diagonal travel, and by the run constant for the run. For 45°, travel = offset × 1.414 and run = offset × 1.000.
What is the 45 degree offset multiplier?
Travel 1.414, run 1.000. A 10″ offset needs 14.14″ of travel between the fittings.
What are the 22.5 and 30 degree multipliers?
30°: travel 2.000, run 1.732. 22.5°: travel 2.613, run 2.414. 60°: travel 1.155, run 0.577.
Is PlumbCalc Pro free?
Yes — the core calculators are free in your browser with no signup; an optional one-time PRO purchase unlocks advanced tools.