What changes at 45 degrees
With 45 degree fittings, the travel is the true offset times 1.414. The run is the true offset times 1.000. Every inch of true offset costs 0.414 inch of length in a bent conduit run (shrink).
- Travel = true offset x 1.414
- Run = true offset x 1.000
- Shrink per inch of offset = 0.414 in
Why 45 degree fittings are the default
A 45 degree fitting is easy to find in every pipe material. It also gives one handy fact: the run equals the true offset. If the true offset is 15 inches, the offset uses up 15 inches of straight pipe.
It turns the flow less than a 90 degree fitting, and it needs less room than a 22.5 degree fitting.
Worked example
Rise 12 inches, roll 9 inches, 3/4 inch copper. True offset is 15 inches. Travel is 21 3/16" (21.21). The 45 degree copper take-off is 11/32 inch, so the cut length is 20 1/2" (20.53).
Pick the pipe type and size in the tool to subtract the fitting take-off and get the cut length.
Rise and roll pairs at 45 degrees
These pairs give a whole number for the true offset, so you can check your own math against them.
| Rise | Roll | True offset | Travel at 45° | Run at 45° |
|---|---|---|---|---|
| 3" | 4" | 5.00" | 7 1/16" (7.07) | 5" (5.00) |
| 6" | 8" | 10.00" | 14 1/8" (14.14) | 10" (10.00) |
| 5" | 12" | 13.00" | 18 3/8" (18.38) | 13" (13.00) |
| 12" | 9" | 15.00" | 21 3/16" (21.21) | 15" (15.00) |
| 8" | 15" | 17.00" | 24 1/16" (24.04) | 17" (17.00) |
| 24" | 7" | 25.00" | 35 3/8" (35.36) | 25" (25.00) |
Compare with the other angles
The offset is the same. Only the fitting angle changes. A smaller angle makes a longer travel and a longer run.
| Angle | Multiplier | Travel | Run | Shrink |
|---|---|---|---|---|
| 22.5° | 2.613 | 39 3/16" (39.20) | 36 3/16" (36.21) | 3" (2.98) |
| 30° | 2.000 | 30" (30.00) | 26" (25.98) | 4" (4.02) |
| 45° | 1.414 | 21 3/16" (21.21) | 15" (15.00) | 6 3/16" (6.21) |
| 60° | 1.155 | 17 5/16" (17.32) | 8 11/16" (8.66) | 8 11/16" (8.66) |
Questions
What is the multiplier for a 45 degree rolling offset?
It is 1.414. Multiply the true offset by it to get the travel.
Why is the run equal to the true offset at 45 degrees?
The tangent of 45 degrees is 1. Run is the true offset divided by that tangent, so the two are equal.
How much shrink does a 45 degree bend in conduit cause?
About 3/8 inch for each inch of true offset (exactly 0.414).