Is there any converter that turns an STL into a proper CAD model?

No. The features and exact surfaces were destroyed when the mesh was made, so there is nothing to convert back to. Reverse-engineering tools fit surfaces to regions of a mesh with human guidance, which is a different and much slower process.

How do I import an STL into SolidWorks?

File, Open, choose the STL, then Options and set Import as: Solid Body. There is a facet-count limit around 20,000, so a detailed mesh usually needs decimating in MeshLab or Blender first.

What can I do with a faceted solid?

Cut it, measure it, reference it, boolean it, put it in an assembly. That covers most practical work like designing a bracket to fit a scanned part. What you cannot do is edit it parametrically or machine from it to tolerance.

Is it faster to remodel it?

For a part of moderate complexity, often yes — an hour or two of measuring and rebuilding gives you a real parametric model instead of an approximation. And if the original exists somewhere, asking for a STEP file takes fifteen seconds.

Convert STL to SLDPRT

This is the direction that does not work, and it is worth understanding why rather than being told no. The information a SolidWorks part contains was destroyed when the STL was written, and nothing can recover it — but there is a workaround that is genuinely useful for some jobs.

We cannot write .sldprt files, and neither can anything except SolidWorks. More fundamentally, no tool anywhere converts a mesh into a properly parametric CAD part — the features and exact surfaces are not in the file to recover. What follows is what is actually achievable.

What was lost, and why it cannot come back

A SolidWorks part is a recipe. It records that you drew a rectangle, extruded it 40 mm, put a 5 mm fillet on four edges, then cut a 6 mm hole 12 mm from one end. Change the 40 to 50 and everything rebuilds, because the model is those instructions rather than the shape they produce.

An STL is the shape they produce, flattened into triangles. The cylinder that was a hole is now sixty flat strips. The fillet is a band of triangles. There is nothing recording that any of it was ever a hole or a fillet, or that the rectangle was 40 mm rather than 39.97.

So converting back is not a matter of a better algorithm. It is asking for information that is not in the file. A tool could guess that sixty strips arranged in a ring were probably meant to be a cylinder, and sometimes guess right — that is what reverse engineering software does — but it is inference, not conversion, and it needs a person to confirm each guess.

This is the same reason a JPEG cannot be turned back into the layered file it was flattened from. The flattening was the lossy step.

The faceted solid workaround, and what it gives you

SolidWorks will import an STL and convert it into a solid body. Every triangle becomes a planar face, so a model with 40,000 triangles arrives as a solid with 40,000 faces.

The path is Open, choose the STL, then Options, and set Import as: Solid Body. There is a limit — SolidWorks refuses meshes above a certain facet count for solid import, typically around 20,000 — so a fine STL usually has to be decimated first, in MeshLab or Blender.

What you get is a real solid body. You can cut it with a plane, measure between faces, use it as a reference for new geometry, boolean it with something you have modelled, and put it in an assembly. That covers a lot of practical work: fitting a bracket to a scanned part, designing a case around a component someone sent you as a mesh, checking clearances.

What you do not get is anything editable in the parametric sense. There is no feature tree, no dimension to change, no fillet to adjust. The cylinder is still sixty flat faces, so a hole you try to measure gives you a slightly different answer depending on which pair of faces you measure between.

When the workaround is not enough

If the part has to be manufactured to tolerance, a faceted solid is not acceptable — a machined surface made from sixty flat strips is sixty flat strips. If the model needs to be modified parametrically, there is nothing to modify. If the surfaces need to be genuinely smooth for a mould or a flow analysis, faceting is exactly the thing you cannot have.

For those, the answer is to remodel. Import the mesh as a reference, measure it, and build a clean parametric model on top of it. For a part of moderate complexity this is usually an hour or two, and the result is a real CAD model rather than an approximation of one.

The commercial reverse-engineering tools — Geomagic, Fusion 360’s Mesh workspace, SolidWorks ScanTo3D — automate parts of this by fitting recognised surfaces to regions of the mesh. They help and they are not magic: someone still has to tell the software which region is meant to be a cylinder.

The much better answer, wherever it is available, is to not be in this situation: ask whoever has the original for a STEP file. Fifteen seconds of their time replaces two hours of yours.

What this site does

Both directions work here now. A STEP file converts to STL, OBJ, GLB, 3MF, PLY or SVG, and an STL, OBJ, PLY, GLB, 3MF or SVG converts back into a STEP solid — in your browser, with nothing uploaded.

The writer does the honest version of the workaround above: the triangles are built into flat faces inside a valid STEP file, which SolidWorks and every other CAD program opens as a faceted solid. You do not need SolidWorks to do the import, and there is no facet-count limit to work around first.

It also does one thing the SolidWorks import does not. Triangles lying in the same plane are merged back into single faces before anything is written, so a flat panel cut into two hundred triangles becomes one face rather than two hundred. That is the difference between a file with forty thousand faces and one with four hundred, and it is what decides whether the result is workable afterwards.

It is described as exactly that on the page, because a tool that promised "STL to CAD" and delivered a faceted solid would be misleading in a way that costs people real time. What is not offered, here or anywhere honest, is mesh to parametric feature tree. It is not a thing software does.

Questions

Is there any converter that turns an STL into a proper CAD model?: No. The features and exact surfaces were destroyed when the mesh was made, so there is nothing to convert back to. Reverse-engineering tools fit surfaces to regions of a mesh with human guidance, which is a different and much slower process.
How do I import an STL into SolidWorks?: File, Open, choose the STL, then Options and set Import as: Solid Body. There is a facet-count limit around 20,000, so a detailed mesh usually needs decimating in MeshLab or Blender first.
What can I do with a faceted solid?: Cut it, measure it, reference it, boolean it, put it in an assembly. That covers most practical work like designing a bracket to fit a scanned part. What you cannot do is edit it parametrically or machine from it to tolerance.
Is it faster to remodel it?: For a part of moderate complexity, often yes — an hour or two of measuring and rebuilding gives you a real parametric model instead of an approximation. And if the original exists somewhere, asking for a STEP file takes fifteen seconds.

Where to go next

Related guides

Tools that do part of this here

About these formats

Checked against current software versions on 2026-09-11