Convert STL to DWG

What people usually mean by this

Almost everyone searching for this wants one of two things, and they are quite different.

A 2D drawing of the part — an outline or a section, to put on a drawing sheet, to dimension, or to send to a laser cutter or waterjet. This is very achievable, and it is a conversion this site does today: a cross-section or outline of a mesh, written as SVG at true size. SVG imports into AutoCAD, and DXF — which is coming here — imports more cleanly still.

A 3D CAD model of the part, editable in AutoCAD. This is the hard direction, and it is the same problem as STL to SLDPRT: the exact surfaces and the modelling history were destroyed when the mesh was made and cannot be recovered. What is achievable is a faceted solid, where each triangle becomes a flat face.

Working out which of the two you need decides everything that follows, and people frequently ask for the second when the first is what they actually want.

If you want a 2D drawing

Take a cross-section or an outline of the mesh and write it as a vector drawing. That is exactly what the STL to SVG converter here does: choose whether you want the silhouette down an axis or a cut at a particular height, and get closed paths at the model’s true size with the unit written into the file.

AutoCAD imports SVG through the MARKUP or ATTACH workflows, and most people go via DXF instead because it drops straight in as native geometry. DXF output is arriving here in a later phase; until then, Inkscape opens the SVG and saves a DXF in two clicks, and it is free.

For a laser cutter or waterjet, you may not need DWG at all — most cutting software takes SVG or DXF directly, and DWG is often just what the shop asked for out of habit.

If you want a 3D model in AutoCAD

AutoCAD will import a mesh. The command is MESHIMPORT for STL, and the result is a mesh object rather than a solid. CONVTOSOLID turns a closed mesh into a 3D solid, with every triangle becoming a face, and it is fussy: the mesh must be watertight and it must not be too large, or the command fails or takes a very long time.

That gives you the faceted solid, which is genuinely useful for positioning, measuring and referencing, and is not an editable CAD model. The cylinder that was a hole is still a ring of flat faces.

You can also skip AutoCAD for that step. This site converts an STL straight into a STEP solid in the browser, merging flat regions into single faces on the way, and AutoCAD imports STEP without the facet-count trouble a mesh import brings.

If the part originated in CAD somewhere, the right move is to find that original and ask for a STEP file. It takes the sender seconds and gives you exact surfaces instead of an approximation.

If it originated as a scan or a sculpt and there is no CAD original, then the choice is between working with the faceted solid and remodelling the part properly from measurements. For anything that will be manufactured to tolerance, remodelling is the honest answer.

Why DXF is the format to aim for

DXF was published by Autodesk specifically so other software could exchange drawings with AutoCAD. It carries the same 2D entities as DWG — lines, arcs, circles, polylines, splines, layers, blocks — in a documented text format, and AutoCAD opens it as native geometry with no import step worth mentioning.

For the 2D case, a DXF is not a compromise. It is the same drawing. The only thing DWG has over it is that it is the native save format, which matters for the person who owns the drawing and not for the person receiving it.

DXF read and write are planned here, which will make STL to DXF a direct conversion for the cross-section and outline cases. The 3D direction will still not become possible, for the reasons above.