Convert 3DS to STEP
Convert 3DS to STEP. This is the one conversion on this site that runs on a server, because rebuilding a solid from triangles needs more than a browser can do. Your file is deleted within an hour.
Result
Before you convert: what this keeps and what it destroys
Preserved
- The shape, as planar faces built from the triangles
- Overall dimensions and proportions
- Watertightness, where the input is watertight
- The unit, recorded in the file
- Colour
- Separate parts and their positions
Destroyed
- Cones, spheres, tori and NURBS, rebuilt as planar facets
Why people convert 3DS to STEP
Rescuing geometry from a format that predates almost everything, usually because an old model library or a supplier's download page is the only source and somebody now needs CAD geometry.
Manage your expectations. 3DS holds triangles written for 3D Studio for DOS. This conversion merges coplanar triangles into planar faces and builds a solid from them, so what you get is faceted reference geometry with no curves, no NURBS and no feature tree.
Two 3DS quirks shape the result. The format caps a mesh at 65,536 vertices, so a detailed model was split into several meshes when it was written and those merge here. And there is no unit anywhere in the file, so the STEP is written in assumed millimetres. Check the dimensions before anybody machines from it.
What you get
You get a plain-text STEP file you can open in an editor containing a boundary representation: planar faces, shared edges and, where the input was closed, a closed shell that CAD software will treat as a solid. Triangles that lay in the same plane are merged into single faces, so a flat side that arrived as two hundred triangles leaves as one face.
Carried across: the unit, recorded in the file, supported base or vertex colour, the supported part structure.
This conversion runs on a server. The upload is deleted within an hour, and nothing about you is recorded alongside it: no IP address, no filename, no account.
What to check afterwards
- 3DS carries no unit. The numbers in the file are just numbers, so the conversion assumes millimetres. Check the overall dimensions of the result before you commit to machining or printing it. A file exported from a package set to inches will be 25.4 times out.
- This is a reconstruction, not a recovery. Coplanar triangles are merged into planar faces and the result is a real solid, but cones, spheres, tori and NURBS surfaces are not recovered and there is no feature tree. Use it as reference geometry.
If you need something this conversion cannot give you
If you need a parametric model, use the original CAD file or remodel the part using this output as reference. Surface fitting can create new geometry, but a mesh does not contain the original sketches or feature history.
Going the other way
This site reads 3DS but does not write it. For the reverse conversion, use an application that can export 3DS.
How we know this conversion works
This pair was checked against 3 files from the test corpus on 2026-09-04. Each run parses its own output back in and compares the bounding box, the triangle count and, for closed solids, the volume against the input.
A pair that fails those checks doesn't get a page. That's why this site lists 120 conversions and not the several hundred a format-times-format grid would suggest.