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STEP to STL Converter

Convert STEP, IGES and BREP CAD files to STL for 3D printing, with the tessellation quality under your control: pick a preset or set the exact deviation and angle, keep assemblies as one file or one STL per part, and read the model's size, volume and part count before you download.

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Drop a STEP file here or click to browse
STEP, STP, IGES, IGS, BREP · up to 200 MB
Choose CAD file
1
Upload STEP / IGES
2
Choose quality
3
Download STL
Mesh quality

Same as the default STL export of most CAD tools: 0.05 mm deviation, holes and fillets stay round at print scale.

Server-sideProcessed on our server, then deleted

Your file is uploaded to our server to be processed, so it does leave your device. Temporary files are removed as soon as processing finishes, and the uploaded original is deleted automatically within 120 minutes at the latest. Nothing is stored permanently.

About

STEP files hold exact geometry: cylinders, fillets and splines as mathematical surfaces. STL holds triangles. Converting one into the other means choosing how closely the triangles follow the surfaces, and that choice is what most online converters hide: they pick one coarse setting and round holes come out as polygons. This tool exposes it. Draft, Standard, Fine and Ultra presets set the linear deviation (the largest gap between the true surface and the mesh, in millimetres) and the angular deviation (the largest angle between neighbouring facets), the same two numbers SolidWorks, Fusion 360, Onshape and FreeCAD ask for at export. Custom lets you type your own, in millimetres or as a fraction of the part's size.

Standard is 0.05 mm and 11.5°, which matches the default export of most CAD packages and keeps a 3 mm hole round at any print resolution. Fine (0.01 mm, 5.7°) is for resin printers and small detailed parts; Draft (0.1 mm, 28.6°) is for checking fit quickly; Ultra (0.002 mm, 2.9°) is below anything a printer resolves and exists for reference geometry. The result panel shows the triangle count and file size, so you can see what the choice cost and try another one.

Assemblies are handled as assemblies. The parts are read with their names, placements and colours through OpenCascade's XCAF layer; you get one merged STL with every part in its place, and optionally a ZIP with one STL per part, plus a GLB that keeps the names and colours for viewers and web use. Units are normalised: whether the file was saved in millimetres, inches or metres, the STL is written in millimetres and the report tells you what the source said. The report also lists solids, shells and faces, the bounding box, the volume and whether any surface had to be healed before meshing.

The converter runs OpenCascade 8.0.1, built from source with the 2026 parser fixes, inside a container with no network access and hard limits on memory and time, because CAD files are complex inputs. Uploads up to 200 MB. Your file and the result are deleted after the download. One conversion up to 50 MB a day is free; a credit pack, a 24-hour pass or a subscription covers the rest, shared with the STL Compressor and the other 3D tools.

How it works

  1. 1Open STEP to STL Converter and choose your file or enter the required input.
  2. 2Check the settings and start the process.
  3. 3The tool creates the result with temporary server-side processing.
  4. 4Download the output or copy the result when it is ready.

FAQ

›Which quality should I pick?
Standard for almost everything you print on an FDM machine: it matches what your CAD program would export by default. Fine for resin or parts under 30 mm with small features. Draft when you only need to check that something fits. Ultra only if you have a reason; it makes files ten to fifty times bigger than Standard for no visible gain on a print.
›Why do my holes look like polygons in other converters?
Because they mesh with a loose angular deviation. A circle is split into facets every N degrees; at 28° a hole is a decagon, at 11.5° it has 31 sides and prints round. Standard and finer keep holes round; Draft does not, on purpose.
›Does it handle assemblies and inches?
Yes. Every part is read with its placement, so the merged STL has the assembly in its assembled position, and you can also get one STL per part in a ZIP. Lengths are converted to millimetres whatever the file's unit; the report shows the unit the file declared.
›Which STEP versions are supported?
AP203, AP214 and AP242, which is every STEP file exported by current CAD software, plus IGES 5.x and OpenCascade BREP. The report shows the schema the file used.
›Can I convert STL back to STEP?
Not here. STL has no surfaces, only triangles, so an STL-to-STEP conversion can only produce a faceted solid with one planar face per triangle, which is rarely useful in CAD. That is a reverse-engineering task, not a file conversion.
›The result says some faces could not be tessellated.
The file has surfaces that are corrupt or have inconsistent trimming, usually from a bad export. The converter heals what it can and tells you how many faces are missing; open the STL in a viewer and check those areas. Re-exporting from the CAD tool as AP214 or AP242 usually fixes it.
›Is my CAD file safe?
It is processed in an isolated container with no network access, by a converter built from the current OpenCascade source, and deleted together with the result after your download. Nothing is kept or shared.