FabCalc - Sheet Metal Flat Pattern Development Calculator

FabCalc calculates flat pattern developments for 14 standard sheet metal fabrication shapes used across pipe fitting, boilermaking, and HVAC trades. From pipe elbows and lobsterback bends to tee junctions, frustum cones, square-to-round transitions, and dome ends.

Flat Pattern Development

Ordinate and piece layout modes with true length calculations at every division point. Seam allowance built in. Export 1:1 PDF templates or DXF files for CNC plasma and laser cutting. Full calculation steps shown so you can verify the maths.

3D Interactive Preview

Full interactive 3D preview with solid, wireframe, and transparent rendering modes. Rotate, zoom, and inspect from any angle. Unfold animation shows the development in real time. Colour-coded segments match your flat pattern.

Workshop Reference Tools

ASME B36.10/B36.19 pipe schedule tables, bend allowance calculator with 8 materials and 3 tempers, bidirectional unit converter (mm, decimal inches, fractional inches to 1/16). Weight calculator with 10 materials and standard sheet size fitting.

14 Fabrication Shapes

Elbow, Lobsterback, Tee, Incline Tee, Tee Hole Cut-Out, Trunnion, Tee to Reducer, Y Branch, Frustum Cone, Flat Back Cone, Oblique Cone, Square to Round, Oblique Square to Round, and Dome End. Each with precise geometric calculations using parallel line development, radial line development, or triangulation methods.

Free Download

FabCalc is free to download on iOS and Android. No account required. Works 100% offline. Built for the workshop.