Using this calculator
Lay out a round branch with two centered, square copes between parallel circular rails.
How to use it
Enter actual outside diameters for both rails and the branch, rail center spacing and the axial gap at each end. The branch diameter must not exceed either rail diameter.
Understanding the results
Review the longest and shortest finished lengths, each cope depth, wrap circumference and 15-degree layout marks. Align the top and bottom marks with zero degrees along the rail axis.
Can I calculate angled or offset joints?
This version supports centered 90-degree joints only. It does not support skewed rails, offset connections, oval tube or arbitrary intersection angles.
Scope and limitations
Dimensions describe the outside surfaces. Bevel and wall-thickness compensation are excluded. The gap is axial, not a constant clearance normal to the mating surface; allow trimming stock and check fit before welding.