The free STL to STEP Converter
Convert STL, OBJ, 3MF or PLY meshes to a STEP (AP214) solid. Welds and repairs the mesh, merges coplanar triangles into true planar faces.
- Free to use
- No signup
- Nothing to install
- Runs in your browser
A 20 mm cube STL (12 triangles) becomes a STEP with 6 planar faces. A faceted 720-triangle sphere becomes 384 planar faces (quads merge where triangles are coplanar). Re-reading both with OpenCascade returns volumes within 0.01% of the original mesh.Open the STL to STEP Converter
Illustration. Open the tool for the real thing.
What is the STL to STEP Converter?
Turning an STL into STEP is one of the most requested and least-served CAD conversions. An STL is just triangles; a STEP solid is made of faces, edges and vertices. This tool builds a genuine STEP AP214 boundary-representation solid from your mesh: it welds duplicate vertices, optionally repairs holes and flipped normals, merges neighbouring coplanar triangles into single planar faces, and writes a closed shell of planar faces that CAD programs import as a real solid body.
Be realistic about what this can do: a mesh describes curved surfaces as many flat facets, so a cylinder becomes a faceted prism in CAD — the tool cannot recover the original cylinder. But for blocky mechanical parts (brackets, enclosures, plates) the planar-face merge returns a clean, light solid, and for any mesh you get a watertight solid you can measure, section, boolean and use as a reference in Onshape, Fusion 360, SolidWorks or FreeCAD. You can verify the output with the built-in OpenCascade check.
3 steps to your result
Open the tool and follow along. Nothing to install.
What you get
ADVANCED_FACE + PLANE + EDGE_CURVE geometry with a closed shell — not just points.
A cube becomes 6 faces, not 12 triangles; large flat areas stay single faces.
Welds vertices, fixes flipped normals and fills small holes before building the solid.
Re-reads the STEP with the OpenCascade kernel and compares face count and volume.
AZRS tools are free to open and use.
It opens in your browser, so there is nothing to download.
Used for
Pick one to see how it fits.
Makers with only an STL of a part
Bring it into CAD as a solid to add holes, mounts or tolerances.
Try it freeEngineering students
Use scanned or downloaded meshes as references in assemblies.
Try it freeReverse-engineering hobbyists
Create a measurable solid from a mesh as a starting point.
Try it freeHow it compares
A plain look at this tool next to the usual alternative.
| This 3d tool | Desktop software | |
|---|---|---|
| Install | Nothing to install | Usually an app or program to install |
| Account | No signup | Depends on the product |
| Cost | Free to use | Free or paid, depends on the product |
| Where it runs | In your browser tab | On your computer |
Questions people ask
Does it make an editable parametric model?
No. It makes a faceted B-rep solid (planar faces). Parametric history and true curves cannot be recovered from a mesh.
Which CAD programs open the result?
Anything that reads STEP AP214: Onshape, Fusion 360, SolidWorks, Inventor, FreeCAD and more — the geometry is standard ADVANCED_FACE/PLANE B-rep.
Why did my STL become so many faces?
Curved surfaces are made of many small facets. Reduce the triangle count of the STL before converting.
Is it safe to upload confidential parts?
Nothing is uploaded; the entire conversion runs in your browser.
How do I know the STEP is valid?
Use the Verify button, which loads the STEP into the OpenCascade CAD kernel and compares the solid with your mesh.
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Try the STL to STEP Converter now
Turn an STL mesh into a STEP B-rep solid with planar faces. Free to use.
Try it free