A rolling offset moves a pipe up or down (the set, or rise) and sideways (the roll) at the same time with one pair of fittings. Looking along the pipe, set and roll are the legs of a right triangle and its diagonal is the true offset. From there it works like a simple offset: travel = true offset × the fitting's travel multiplier, run = true offset × the run multiplier.
All values are centerline, center to center. For a cut length, subtract each fitting's take-out from the travel and verify with your fitting's dimensions: take-outs vary by maker and pipe type. For any other set, roll or angle, the Rolling Offset calculator in the TrueOffset app works it out offline and also shows how far to roll the fittings.
Rolling offset formula
True offset = √(set² + roll²). For fitting angle A, travel = true offset × 1 ÷ sin A (the travel multiplier) and run = true offset × cot A, that is true offset ÷ tan A (the run multiplier). Roll the fittings arctan(roll ÷ set) off vertical. The multipliers go on the true offset, never on the set or the roll alone.
Travel and run multipliers| Fitting angle | Travel multiplier | Run multiplier |
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| 22½° | 2.613 | 2.414 |
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| 45° | 1.414 | 1.000 |
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| 60° | 1.155 | 0.577 |
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Worked example: 12" set, 9" roll, 45° fittings
True offset = √(12² + 9²) = √(144 + 81) = √225 = 15". Travel = 15 × 1.414 = 21.21", which is 21 3/16" to the nearest 1/16". Run = 15 × 1.000 = 15". Roll the fittings arctan(9 ÷ 12) = 36.9° off vertical.
The same offset with 22½° fittings: travel 15 × 2.613 = 39.20" (39 3/16"), run 15 × 2.414 = 36.21" (36 3/16"). With 60° fittings: travel 15 × 1.155 = 17.32" (17 5/16"), run 15 × 0.577 = 8.66" (8 11/16").
45° rolling offset chart
True offset and travel with 45° fittings; at 45° the run equals the true offset. Only roll ≤ set is listed: the other way round, swap them, because true offset, travel and run stay the same (only the roll angle changes). When set and roll are equal, the 45° travel is exactly twice the set: 12" and 12" give 24".
45° fittings: true offset and travel (run = true offset)| Set (rise) | Roll | True offset | Travel |
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| 2" | 2" | 2 13/16" | 4" |
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| 3" | 2" | 3 5/8" | 5 1/8" |
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| 3" | 3" | 4 1/4" | 6" |
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| 4" | 2" | 4 1/2" | 6 5/16" |
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| 4" | 3" | 5" | 7 1/16" |
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| 4" | 4" | 5 11/16" | 8" |
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| 6" | 2" | 6 5/16" | 8 15/16" |
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| 6" | 3" | 6 11/16" | 9 1/2" |
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| 6" | 4" | 7 3/16" | 10 3/16" |
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| 6" | 6" | 8 1/2" | 12" |
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| 8" | 2" | 8 1/4" | 11 11/16" |
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| 8" | 3" | 8 9/16" | 12 1/16" |
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| 8" | 4" | 8 15/16" | 12 5/8" |
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| 8" | 6" | 10" | 14 1/8" |
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| 8" | 8" | 11 5/16" | 16" |
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| 9" | 2" | 9 1/4" | 13 1/16" |
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| 9" | 3" | 9 1/2" | 13 7/16" |
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| 9" | 4" | 9 7/8" | 13 15/16" |
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| 9" | 6" | 10 13/16" | 15 5/16" |
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| 9" | 8" | 12 1/16" | 17" |
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| 9" | 9" | 12 3/4" | 18" |
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| 12" | 2" | 12 3/16" | 17 3/16" |
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| 12" | 3" | 12 3/8" | 17 1/2" |
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| 12" | 4" | 12 5/8" | 17 7/8" |
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| 12" | 6" | 13 7/16" | 19" |
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| 12" | 8" | 14 7/16" | 20 3/8" |
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| 12" | 9" | 15" | 21 3/16" |
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| 12" | 12" | 17" | 24" (2' 0") |
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| 16" | 2" | 16 1/8" | 22 13/16" |
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| 16" | 3" | 16 1/4" | 23" |
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| 16" | 4" | 16 1/2" | 23 5/16" |
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| 16" | 6" | 17 1/16" | 24 3/16" (2' 3/16") |
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| 16" | 8" | 17 7/8" | 25 5/16" (2' 1 5/16") |
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| 16" | 9" | 18 3/8" | 25 15/16" (2' 1 15/16") |
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| 16" | 12" | 20" | 28 5/16" (2' 4 5/16") |
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| 16" | 16" | 22 5/8" | 32" (2' 8") |
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| 18" | 2" | 18 1/8" | 25 5/8" (2' 1 5/8") |
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| 18" | 3" | 18 1/4" | 25 13/16" (2' 1 13/16") |
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| 18" | 4" | 18 7/16" | 26 1/16" (2' 2 1/16") |
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| 18" | 6" | 19" | 26 13/16" (2' 2 13/16") |
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| 18" | 8" | 19 11/16" | 27 7/8" (2' 3 7/8") |
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| 18" | 9" | 20 1/8" | 28 7/16" (2' 4 7/16") |
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| 18" | 12" | 21 5/8" | 30 5/8" (2' 6 5/8") |
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| 18" | 16" | 24 1/16" (2' 1/16") | 34 1/16" (2' 10 1/16") |
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| 18" | 18" | 25 7/16" (2' 1 7/16") | 36" (3' 0") |
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| 24" | 2" | 24 1/16" (2' 1/16") | 34 1/16" (2' 10 1/16") |
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| 24" | 3" | 24 3/16" (2' 3/16") | 34 3/16" (2' 10 3/16") |
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| 24" | 4" | 24 5/16" (2' 5/16") | 34 7/16" (2' 10 7/16") |
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| 24" | 6" | 24 3/4" (2' 3/4") | 35" (2' 11") |
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| 24" | 8" | 25 5/16" (2' 1 5/16") | 35 3/4" (2' 11 3/4") |
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| 24" | 9" | 25 5/8" (2' 1 5/8") | 36 1/4" (3' 1/4") |
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| 24" | 12" | 26 13/16" (2' 2 13/16") | 37 15/16" (3' 1 15/16") |
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| 24" | 16" | 28 7/8" (2' 4 7/8") | 40 13/16" (3' 4 13/16") |
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| 24" | 18" | 30" (2' 6") | 42 7/16" (3' 6 7/16") |
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| 24" | 24" | 33 15/16" (2' 9 15/16") | 48" (4' 0") |
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22½° and 60° rolling offsets
Travel and run for the same kind of offsets with 22½° and 60° fittings. Example: 16" set and 12" roll make a 20" true offset; with 22½° fittings the travel is 20 × 2.613 = 52.26" (52 1/4") and the run 20 × 2.414 = 48.28" (48 5/16").
22½° fittings: travel and run| Set (rise) | Roll | Travel | Run |
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| 4" | 4" | 14 13/16" | 13 11/16" |
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| 6" | 4" | 18 13/16" | 17 7/16" |
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| 6" | 6" | 22 3/16" | 20 1/2" |
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| 9" | 4" | 25 3/4" (2' 1 3/4") | 23 3/4" |
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| 9" | 6" | 28 1/4" (2' 4 1/4") | 26 1/8" (2' 2 1/8") |
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| 9" | 9" | 33 1/4" (2' 9 1/4") | 30 3/4" (2' 6 3/4") |
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| 12" | 4" | 33 1/16" (2' 9 1/16") | 30 9/16" (2' 6 9/16") |
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| 12" | 6" | 35 1/16" (2' 11 1/16") | 32 3/8" (2' 8 3/8") |
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| 12" | 9" | 39 3/16" (3' 3 3/16") | 36 3/16" (3' 3/16") |
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| 12" | 12" | 44 3/8" (3' 8 3/8") | 41" (3' 5") |
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| 16" | 4" | 43 1/8" (3' 7 1/8") | 39 13/16" (3' 3 13/16") |
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| 16" | 6" | 44 5/8" (3' 8 5/8") | 41 1/4" (3' 5 1/4") |
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| 16" | 9" | 48" (4' 0") | 44 5/16" (3' 8 5/16") |
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| 16" | 12" | 52 1/4" (4' 4 1/4") | 48 5/16" (4' 5/16") |
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| 16" | 16" | 59 1/8" (4' 11 1/8") | 54 5/8" (4' 6 5/8") |
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| 24" | 4" | 63 9/16" (5' 3 9/16") | 58 3/4" (4' 10 3/4") |
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| 24" | 6" | 64 5/8" (5' 4 5/8") | 59 3/4" (4' 11 3/4") |
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| 24" | 9" | 67" (5' 7") | 61 7/8" (5' 1 7/8") |
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| 24" | 12" | 70 1/8" (5' 10 1/8") | 64 3/4" (5' 4 3/4") |
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| 24" | 16" | 75 3/8" (6' 3 3/8") | 69 5/8" (5' 9 5/8") |
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| 24" | 24" | 88 11/16" (7' 4 11/16") | 81 15/16" (6' 9 15/16") |
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60° fittings: travel and run| Set (rise) | Roll | Travel | Run |
|---|
| 4" | 4" | 6 9/16" | 3 1/4" |
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| 6" | 4" | 8 5/16" | 4 3/16" |
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| 6" | 6" | 9 13/16" | 4 7/8" |
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| 9" | 4" | 11 3/8" | 5 11/16" |
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| 9" | 6" | 12 1/2" | 6 1/4" |
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| 9" | 9" | 14 11/16" | 7 3/8" |
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| 12" | 4" | 14 5/8" | 7 5/16" |
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| 12" | 6" | 15 1/2" | 7 3/4" |
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| 12" | 9" | 17 5/16" | 8 11/16" |
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| 12" | 12" | 19 5/8" | 9 13/16" |
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| 16" | 4" | 19 1/16" | 9 1/2" |
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| 16" | 6" | 19 3/4" | 9 7/8" |
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| 16" | 9" | 21 3/16" | 10 5/8" |
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| 16" | 12" | 23 1/8" | 11 9/16" |
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| 16" | 16" | 26 1/8" (2' 2 1/8") | 13 1/16" |
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| 24" | 4" | 28 1/8" (2' 4 1/8") | 14 1/16" |
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| 24" | 6" | 28 9/16" (2' 4 9/16") | 14 5/16" |
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| 24" | 9" | 29 5/8" (2' 5 5/8") | 14 13/16" |
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| 24" | 12" | 31" (2' 7") | 15 1/2" |
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| 24" | 16" | 33 5/16" (2' 9 5/16") | 16 5/8" |
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| 24" | 24" | 39 3/16" (3' 3 3/16") | 19 5/8" |
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Lengths are rounded to the nearest 1/16" (feet and inches in brackets from 2 ft), multipliers to three decimals and the roll angle to one decimal.
Frequently asked questions
What is the formula for a rolling offset?
True offset = √(set² + roll²); travel = true offset × the travel multiplier (1.414 for 45°, 2.613 for 22½°, 1.155 for 60°); run = true offset × the run multiplier (1.000, 2.414 and 0.577). 12" set and 9" roll with 45s: true offset 15", travel 21 3/16", run 15".
How do you figure a 45 rolling offset?
Square the set and the roll, add them and take the square root for the true offset, then multiply by 1.414 for the travel. The run is the same as the true offset. 16" set and 12" roll: √(256 + 144) = √400 = 20", travel 20 × 1.414 = 28.28" (28 5/16"), run 20".
Can I just multiply the set by 1.414?
No. That is a simple offset: it ignores the roll and comes out short. 12" set and 9" roll: 12 × 1.414 = 16.97" (17"), but the real travel is 15 × 1.414 = 21.21" (21 3/16"). Always multiply the true offset.
How far do you roll the fittings?
Turn them arctan(roll ÷ set) off vertical, toward the roll side. 12" set and 9" roll: arctan(0.75) = 36.9°. Equal set and roll is 45°; no roll is 0° (a plain vertical offset).
Is the travel in the chart the cut length?
No. Travel is fitting center to fitting center. Subtract both fittings' take-outs for the cut length; take-outs vary by maker and pipe type, so verify with your fitting's dimensions. The Pipe Cut Length Calculator does the subtraction.
Estimates only. Check measurements, product labels and local building codes before you buy or build.