Free tool
STL to STEP converter
Drop an STL. Get a STEP solid for your CAD program, written in your browser.
Runs in your browser. Nothing is uploaded.
How to use it
1Drop the mesh
An STL, OBJ, 3MF, GLB or PLY. Each object becomes a part with an edge check, so you see at once whether it is closed.
2Check it is closed
A closed mesh becomes a solid body. A mesh with holes becomes surfaces instead, so repair it first if you need a solid.
3Pick STEP
Choose STEP as the output. Sizes stay in millimetres with Z up, the way the mesh was printed.
4Download and import
Open the .step file in your CAD program as a body you can measure, cut and combine with new features.
To convert an STL to STEP, drop the STL on the converter above, choose STEP as the output and download. A closed mesh becomes a solid body in a standard AP214 STEP file, with one flat face per triangle and every edge shared between neighbouring faces. The conversion runs in your browser; nothing is uploaded.
What an STL to STEP conversion can and cannot do
STEP is the format CAD programs use to exchange exact solids. An STL has already lost that exactness: it is a list of triangles, with no record of which ones were a hole, a fillet or a flat face. So every STL to STEP converter, including this one, produces a faceted solid. The body is closed and measurable, it can be cut, shelled and combined with new features, but its curved areas stay made of flat facets.
That is enough for most jobs that start with a mesh: adding mounting holes to a downloaded model, designing a bracket around a scanned part, or sending a printable model to someone who only works in CAD.
Get a cleaner STEP file
| Problem | Fix before converting |
|---|---|
| Huge file, CAD opens it slowly | Lower the triangle count with the STL simplifier |
| Written as surfaces, not a solid | Close the holes with the STL repair tool |
| Loose fragments around the part | Keep largest shell in the STL editor |
| Wrong size in CAD | Check the unit before converting: STEP is written in millimetres |
Going the other way
To turn a CAD file into something printable, use the STEP to STL converter, which reads STEP and IGES with OpenCascade and keeps every solid as its own part. To look at a STEP file without converting it, open it in the STEP viewer.
Questions
How do I convert an STL to STEP?
Drop the STL on the converter above, choose STEP as the output and download. A closed mesh is written as a solid body in a standard AP214 STEP file, with one flat face for each triangle, entirely in your browser.
Will the STEP file have smooth curves?
No. An STL only stores triangles; it does not remember that a group of them was a cylinder. The STEP keeps those triangles as flat faces. To get true curves back, rebuild the feature in CAD on top of the imported body.
Why is my STEP file so large?
Every triangle becomes a face with its own edges, so a 100,000 triangle mesh makes a very large STEP that CAD programs open slowly. Reduce the triangle count first with the STL simplifier in Depthue Studio, then convert.
Why did I get surfaces instead of a solid?
A STEP solid must be closed. If the mesh has holes or open edges, the converter writes it as surfaces and says so. Repair the mesh with the free STL repair tool, then convert again.
Which CAD programs open the file?
It is a standard AP214 STEP file, the format CAD programs use to exchange solids. Every file is tested by reading it back with OpenCascade, the geometry kernel inside FreeCAD.
Is my file uploaded?
No. The STEP file is written in your browser and downloaded straight from it.
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