Convert STL to STEP
Convert STL 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
Destroyed
- Cones, spheres, tori and NURBS, rebuilt as planar facets
↺ the reverse: STEP → STL · about .stl · about .step · just view it instead
Why people convert STL to STEP
People want this conversion for one of two reasons, and only one of them works.
The one that works: you have a mesh (a scan, a downloaded model, an old STL with no source file) and you need to hand a machine shop something their CAM software will accept, or bring it into CAD as reference geometry to model around. A faceted solid does that job.
The one that doesn't: you're hoping to get an editable, parametric model back. No tool can do that, at any price. The feature tree was thrown away when the STL was written, and a converter can't recover information that isn't in the file.
What you get here is a real B-rep solid: coplanar triangles merged into single planar faces, edges shared between faces, and a closed shell. A cube comes out as six faces instead of twelve triangles. What you don't get is cones, spheres, tori, NURBS surfaces or a feature tree.
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.
This conversion runs on a server rather than in your browser, because rebuilding a solid from triangles needs more memory and time than a browser tab can reliably give it. 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
- STL 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, this conversion cannot give you one and neither can any other tool. The feature tree was destroyed when the mesh was written. Use this output as reference geometry and remodel the part around it.
Going the other way
Convert STEP back to STL is the reverse page. It is not the inverse of this one: reconstructing a solid from triangles produces faceted geometry, and tessellating it again would not return you to where you started.
How we know this conversion works
This pair was checked against 8 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.