Convert STL to STEP
Online

Upload your .stl above and download a .step, with no signup. The converter repairs the mesh first, then rebuilds real planes and cylinders for mechanical parts, or falls back to an honest faceted solid when it cannot. If you would rather do it by hand, FreeCAD does the same job through its Part workbench, and our step-by-step FreeCAD guide covers that route and the one step that usually makes it fail.

Yes. This converter is free and runs in the browser with nothing to install. STP and STEP are the same format with two spellings of the extension, so a file saved as either .stp or .step works here and downloads back as a standard STEP file.

Automatically, within limits that this page is explicit about. A mesh has no record of the surfaces it was tessellated from, so an STL to STEP conversion has to infer them. On prismatic mechanical parts that inference works and you get real planes and cylinders back. On organic or scanned geometry it does not, and rather than guess, the converter hands you a faceted solid and says so in the job console. Nothing here needs you to open a CAD program first.

STP and STEP are two spellings of the same ISO 10303 format, so both work. Upload a .stl and the download is named .step; if your software insists on the three-letter extension, renaming the file to .stp is enough and changes nothing inside it. An stl to stp conversion and a .stl to .step conversion are the same job.

Every one of them can do it and every one of them has the same ceiling, because the missing information is missing in the file, not in the software. Fusion 360 offers Mesh then Convert Mesh, whose parametric mode caps the facet count and refuses dense meshes outright. SolidWorks has ScanTo3D, an add-in that is not enabled on every licence tier. FreeCAD's Part workbench does it free, and our FreeCAD guide walks through the one setting that usually makes it fail. The advantage here is that nothing installs and the honest result is reported rather than hidden.

STL files store geometry as triangles, so there's no concept of 'a cylinder' or 'a flat face' in the format. This makes STL great for 3D printing but impossible to edit parametrically. STEP files store mathematical surface definitions, so you can select a face, change a dimension, add a fillet, or create an engineering drawing. Convert when you need to modify a model in SolidWorks, Fusion 360, FreeCAD, or OnShape.

Dimensionally, as accurate as the mesh itself. Structurally, it depends on the part, and the job console tells you which result you got. For simple mechanical parts (flat faces, straight holes, cylindrical rims), the converter now detects the underlying planes and cylinders and rebuilds them as true analytic CAD surfaces: a hole comes back as a real cylinder you can click and re-dimension. This only happens when three checks pass: the detected surfaces must cover at least 80% of the part, the rebuilt solid's volume must match the mesh within 2%, and sampled mesh points must lie on the rebuilt surface (which catches a wrong shape that happens to match the right volume). If any check fails (fillets, pockets, organic regions, scan noise), you get the standard conversion instead: flat regions merged into planar faces on parts under 19,000 triangles, curved features keeping the mesh's faceting. You never silently get wrong geometry.

Every major CAD program supports STEP (ISO 10303): SolidWorks, Fusion 360, FreeCAD, OnShape, CATIA, Siemens NX, PTC Creo, Autodesk Inventor, and more. STEP is the universal neutral format for CAD exchange. If a program does CAD, it opens STEP.

Yes. Our STEP to STL converter tessellates the mathematical surfaces into a triangle mesh at your chosen resolution. Use this when you have a STEP file from a CAD program and need to 3D print it.

Free accounts: 25MB per file. Files are processed in our cloud and permanently deleted within 24 hours.

The most common cause of poor results is organic or sculpted geometry. Characters, figurines, and freeform surfaces have no flat regions to merge, so the STEP ends up carrying thousands of tiny triangular faces (or the conversion times out). Mechanical parts dominated by flat faces work best. If the mesh has holes or non-manifold edges, our engine attempts automatic repair before converting.

Yes, the converter is free to use. Free accounts get 5 conversions per day with files up to 25MB. Pro accounts get unlimited conversions, larger file sizes, and priority processing.