Multi-Piece Miter Elbow Layout

Per-cut miter angle, weld count, and cutback for an n-piece lobster-back miter elbow.

Run the calculator

Example

You enter

Total turn angle (deg) 90
Number of pieces (>= 2) 3
Pipe outside diameter (in) 12.75

You get

Miter angle per cut (deg) 22.5
Cutback (in) 5.2812
Welds (cuts) 2

Details, formula, and sources

For an n-piece miter turning total angle A: n-1 cuts (welds); cut angle theta = A/(2*(n-1)) from square; cutback = OD * tan(theta). End pieces are half-gores.

Multi-piece (lobster-back) miter-elbow geometry - the per-cut miter angle A/(2*(n-1)) and the OD*tan(theta) cutback - as taught in NCCER Pipefitting and the standard fabrication references, by name; first-principles geometry.

Public first-principles geometry. The welding procedure, the bevel, and the engineer of record govern the fabricated fitting.

Estimate. AHJ and licensed professional govern.

Field names used by the API: total_angle_deg, pieces, outside_diameter_in, miter_angle_deg, cutback_in, n_welds

Fabrication the welding procedure, bevel, and engineer of record govern the finished fittingfabrication reference