Free tool · Insulation · Pipework
Segmented pipe bend calculator – cutting plan and 1:1 templates
Enter diameter, bend angle, bend radius and number of segments – the calculator returns the segment angle, all segment lengths, the bend in 3D and the templates for full and half segments at 1:1. For lobster-back bends in cladding, ducting, exhaust and pipework. Works in mm or inch.
Open the calculatorSegmented bend calculator
3D preview
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Cutting plan
Flat pattern – full segment
Flat pattern – half segment
0° = back (outside of the bend) · 180° = throat (inside of the bend)
What is a segmented bend?
A segmented bend – also called a lobster-back or mitered bend – replaces a formed elbow with several short, obliquely cut pieces of pipe. It is built wherever no suitable elbow is available or sheet cannot be formed: sheet metal jackets around insulated lines, ventilation and exhaust ducts, or large diameters in plant construction.
Layout: half segments and full segments
The calculator uses the common layout with two half segments at the ends and full segments in between. A 90° bend with 3 full segments has 4 joints of 22.5° each; every joint is cut at 11.25°.
| 90° bend | Segment angle | Cut angle per joint |
|---|---|---|
| 1 full segment | 45° | 22.5° |
| 2 full segments | 30° | 15° |
| 3 full segments | 22.5° | 11.25° |
| 4 full segments | 18° | 9° |
Reading the templates
The 0° line marks the back (outside of the bend), 180° the throat (inside). The segments are joined turned 180° to each other in turn, so that back meets back and throat meets throat.
Help
Frequently asked questions
How is a segmented bend calculated?
With two half segments and n full segments, the segment angle is the bend angle divided by (n + 1). Every joint is cut at half the segment angle. A full segment measures 2 × bend radius × tan(cut angle) on the centerline, a half segment half of that.
Why two half segments at the ends?
This way the bend starts and ends with a square cut and joins the straight pipe cleanly. It is the usual layout in insulation, ducting and pipework.
Which bend radius is typical?
Often 1 to 1.5 times the diameter, measured to the centerline. A larger radius gives a smoother bend with less flow resistance but needs more space.
How many segments should I choose?
The more segments, the rounder the bend. For a 90° bend, 2 to 4 full segments are common. With large diameters or tight radii choose more segments – the individual templates also become flatter.
Does it work for sheet metal jackets on insulated pipe?
Yes. Enter the outside diameter of the jacket and the sheet thickness. Add the overlap or seam allowance to the template length.
Can I get the flat pattern as a DXF file?
Yes. The DXF holds the full segment and the half segment side by side at full scale, each with back and throat curves, so a cladding blank can go straight to the cutting table. Add seam allowances and kerf compensation in your own software.