STLBenchFree online STL to CAD converter
STL to CAD — what a mesh can actually become
Drop a mesh and the page measures it before converting anything: how much of its surface is recognisably planes, cylinders and cones, and how much is free-form and will stay as facets. Then pick the file the destination needs — a STEP solid for a modelling package, a DXF section for a cutter. Machined parts come back as CAD you can dimension; scans do not, and you are told which yours is rather than sold a conversion that disappoints later.
- 100% free
- No signup
- Verdict before conversion
- STEP or DXF
- Nothing uploaded
Drag a file anywhere on this page to open it. F fits the view, W switches shading, G the grid, R spins it.
How to convert STL to CAD
Three steps, and the second one is the reason to use this page.
Drop the mesh
STL, OBJ, PLY, 3MF or GLB. It is welded, its winding made consistent and its degenerate triangles removed first, because a mesh that looks broken is often only a mesh with a few zero-area faces in it.
Read what your file actually is
Recognition runs first and its result is a percentage: the share of the model's surface that turned out to be genuine geometry, against the share that stayed a collection of facets. This is the whole point of the page. A machined part scores high and converts into real CAD; a scan scores low and will not, whatever any converter's landing page says.
Pick the file the destination wants
STEP if it is going into a modelling package as a solid; DXF if the next step is a cutter and what you need is a contour. Both are written here, and neither uploads anything.
Technical specifications
| Reads | .stl, .obj, .ply, .3mf, .glb, .gltf, .fbx |
|---|---|
| Writes | .step — AP214 solid, millimetres; .dxf — R12 section |
| Rebuilds | Planes, cylinders whole or partial, full cones; holes as true circles |
| Not rebuilt | Fillets, spheres, spline surfaces, threads — left as facets |
| Gate | Recognised surface share and verdict shown before converting |
| Best on | Machined and modelled parts: plates, brackets, housings |
| Poor on | Scans, sculpts, organic shapes, threaded fasteners |
| Not produced | A feature tree — conversion gives geometry, never history |
| File size | No fixed limit — past 100 MB you are told what it will cost this tab, then it opens |
Frequently asked questions
What does "CAD" mean as a target?
It is not a format, which is why this conversion confuses people. Asking for CAD usually means one of two concrete things. Either you want a solid with real faces you can dimension and edit — that is STEP, the format every package reads and the closest thing engineering has to a lingua franca. Or you want a flat drawing to cut, in which case it is DXF and the operation is a section rather than a rebuild. Both are here; picking the right one is mostly a question about what happens next.
Can any mesh become CAD?
No, and this is the part that gets glossed over. A mesh is a bag of triangles with no record of what it was tessellated from. If the original was a modelled part, the flat regions and cylindrical strips are still recognisable and can be rebuilt into the surfaces they came from. If the original was a scan, a sculpt or an organic shape, there are no planes and cylinders underneath to recover — the surface really is free-form, and the best any converter can do is wrap the triangles in a STEP file that has the same number of faces as the mesh had triangles.
How do I know which one mine is?
The panel tells you before you convert. It reports the proportion of surface area that was recognised as real geometry and the number of triangles left over, and turns that into a verdict. On ten real test parts the recognised share ranged from 15% to 93% — brackets and housings near the top, printed miniatures at the bottom. Nothing about the file name predicts it; the geometry does.
What about the parts that are not recognised?
They stay as facets, and they are counted. That is a defensible result: a STEP with some rebuilt surfaces and some facet regions still imports, still measures and still positions correctly in an assembly, and it is far better than the alternative of a converter guessing at a surface that is not there. What it will not do is behave like modelled geometry in those areas — you cannot fillet a region that is a hundred flat faces.
Is there a way to get a truly editable model?
Remodelling it, and for a lot of parts that is genuinely the right call. A converted STEP gives you geometry; it does not give you a feature tree, so there is no extrude to change and no hole wizard to edit. What conversion is good for is measuring, fitting a new part to an existing one, and getting a mating surface right. If the goal is a parametric model you will iterate on, the measurements from a converted file are the useful output and the model is still yours to build.
Is my file uploaded?
No. Recognition, conversion and writing all happen in this tab, in a worker thread so the page stays responsive on a large part.
The question behind the search
Almost everybody who looks for this conversion is holding a file somebody sent them and a job that needs a different kind of file. A supplier sent an STL and the fixture has to mate with it. A customer sent a printed part and the replacement has to fit. Somewhere in that there is a real question — can I get engineering geometry out of this? — and the answer depends entirely on what the mesh was before it was a mesh.
The information is genuinely gone. An STL records triangles and nothing else: no faces, no edges, no holes, no dimensions. The wall of a bore is a run of narrow strips with no note anywhere saying they were once one surface. Recovering that is inference, and inference is only ever as good as the evidence in front of it. A machined bracket leaves plenty — broad flat regions, fans of strips sharing an axis. A scanned face leaves none, because there was never a plane or a cylinder there to begin with.
So the useful thing a page like this can do is not convert harder, it is tell you which case you are in, with numbers, before you build a plan around the answer. That is the gate above: recognised surface area, leftover triangles, and a verdict. If it says your part qualifies, the STEP will have real cylindrical faces and holes at their true diameter — measurably more accurate than the mesh it came from, since a faceted bore always measures under the circle it was cut from, and recovering that circle undoes the loss.
If it says it does not, that is worth knowing in five seconds rather than after a hundred-megabyte download. The deeper explanation of how the rebuilding works is on STL to STEP, the SolidWorks-specific route — and why its own STL import gives you something you cannot edit — is on STL to SolidWorks, and if what you need is flat, STL to DXF sections the model where you choose.
Where the conversion happens
Every number on this page is worked out by JavaScript running in the tab you are reading it in. The model you open is read straight off your own disk — it is never uploaded, logged or kept, which is also why these tools carry on working after you disconnect from the network.
Worth naming here: the meshes people bring to this question are usually somebody else's part, held under whatever terms it arrived with. The recognition and the writing both run in this tab, so nothing about it is transmitted anywhere.