Estimates only. Check measurements, product labels and local building codes before you buy or build.
How the Pipe Offset Calculator works
A pipe offset moves a run up, down or sideways so it carries on parallel to where it started, using two fittings of the same angle (two 45s, two 22½s and so on). This calculator gives the two numbers you need to fit it: the travel, the center-to-center length of the angled piece, and the run (also called the advance), how much further along the second fitting sits. Pick 11¼°, 22½°, 30°, 45° or 60°, or type any angle.
It is right-triangle trigonometry on the centerlines. The offset is the side opposite the fitting angle A and the travel is the hypotenuse, so travel = offset ÷ sin A and run = offset ÷ tan A. The numbers 1 ÷ sin A and 1 ÷ tan A are the multipliers on every fitter's chart: 11¼° 5.126 and 5.027, 22½° 2.613 and 2.414, 30° 2.000 and 1.732, 45° 1.414 and 1.000, 60° 1.155 and 0.577.
Example: a 12" offset with two 45° elbows. Travel = 12 × 1.414 = 16.97", which is 17" to the nearest 1/16" (16 31/32" to the nearest 1/32"). Run = 12 × 1.000 = 12". Check: 12² + 12² = 288, and √288 = 16.97, so the travel is the diagonal of the offset and the run.
Both results are center to center: from the centerline of one run to the centerline of the other, and from fitting center to fitting center. To get the length of pipe to cut, subtract the take-out of both fittings (and any weld gaps) from the travel; the Pipe Cut Length Calculator does that step. Take-outs depend on the fitting's size, type and maker, so measure your fitting or use the maker's dimensions. Shallower fittings make a longer offset: at 22½° the run is 2.414 times the offset, at 60° only 0.577 times.
1.414. Multiply the offset by 1.414 for the travel (center to center of the two 45s) and by 1.000 for the run: a 12" offset has a 16.97" (17") travel and a 12" run. 1.414 is 1 ÷ sin 45°, the square root of 2.
What is the offset multiplier for 30 and 60 degree fittings?
30°: travel = offset × 2.000 and run = offset × 1.732. 60°: travel = offset × 1.155 and run = offset × 0.577. A 10" offset is a 20" travel with 30s and an 11.55" (11 9/16") travel with 60s.
What is the multiplier for a 22 1/2 degree offset?
2.613 for the travel and 2.414 for the run. A 10" offset with two 22½° fittings has a travel of 10 × 2.613 = 26.13" (26 1/8") and a run of 10 × 2.414 = 24.14" (24 1/8").
How do I find the offset multiplier for any angle?
Travel multiplier = 1 ÷ sin(angle), run multiplier = 1 ÷ tan(angle). For 15°: 1 ÷ sin 15° = 3.864 and 1 ÷ tan 15° = 3.732, so a 12" offset needs a 46.36" travel and a 44.78" run. Pick Custom and type the angle to get them.
Is a pipe offset measured center to center?
Yes. Measure from the centerline of the pipe you are leaving to the centerline of the pipe you are going to, square to the runs. For two pipes of the same size, top to top or edge to edge gives the same distance.