STEP to STL Converter
Convert STEP (.step, .stp) CAD files to STL for 3D printing, free and in your browser: OpenCASCADE triangulates every solid, units converted to millimetres, with a 3D preview and watertight check. Nothing uploaded.
How it works
Open the STEP file
Drop a .step or .stp file exported from SolidWorks, Fusion 360, Onshape, FreeCAD, Inventor or any CAD program. OpenCASCADE reads it in your browser, in its own units, and converts them to millimetres.
It is cut into triangles
Every face of every solid becomes a mesh, each curve followed to within 5.7 degrees and a thousandth of the part's size. Turn it in 3D and check the size, triangle count and that it is closed.
Download the STL
Pick the format and download: STL or 3MF for the slicer, OBJ for Blender, GLB for the web (turned Y-up and scaled to metres).
STEP to STL converter: free and online
Convert STEP to STL in your browser: drop in a STEP file and download the STL. The file is converted on your own device and never uploaded, so this step to stl converter is safe for private and confidential files.
STL is the 3D printing format: a closed surface of triangles that every slicer reads.
The paths come out at the real size you set, in millimetres or inches, ready for a laser, a CNC router, a vinyl cutter or a plotter.
More conversions from STEP: STEP to OBJ, STEP to 3MF, STEP to GLB.
Other conversions to STL: Sketch to STL, SVG to STL, Image to STL, Image to STL, OBJ to STL, GLB to STL.
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Why it matters
The right way up and the right size
A 20 mm part stays 20 mm and upright: glTF's metres and Y-up axis are converted to and from the millimetres and Z-up of STL, 3MF and slicers.
Checked against a reference
Every format pair is tested against trimesh: the same volume, surface area and size come back out.
Nothing uploaded
Client parts and unreleased designs stay on your computer. The model is read and written in this tab.
Questions
How do I convert STEP to STL?
Drop your STEP file on this page, check the preview, and press Download. The STL is made in a few seconds, with no sign-up.
Is my STEP file uploaded anywhere?
No. The step to stl conversion runs in your browser, on your own device. The file never leaves it.
How accurate is the STEP to STL conversion?
The size is exact: units in the file (inches, metres, millimetres) are converted to millimetres, and a 10 mm cube comes out 10.000 mm. Curved faces become flat triangles that follow the true surface to within a thousandth of the part's size; a 10 mm cube with a 5 mm round edge measures 946.27 mm3 against the exact 946.35.
Which STEP and IGES files work?
Solids and surfaces exported as STEP or IGES by CAD programs. The reader is OpenCASCADE, the geometry kernel FreeCAD is built on. A file with several bodies comes in with every body. A file holding only a 2D drawing, curves or points has no surface, and the page says so.
Is my CAD file uploaded?
No. The OpenCASCADE reader (occt-import-js, LGPL) runs in your browser tab, so client parts and unreleased designs never leave your computer.
Which 3D formats can I convert?
STL (binary and ASCII), OBJ, PLY (ASCII and binary), OFF, 3MF, GLB and glTF, in and out, in any combination.
Are colours and textures kept?
No: the shape is converted, every triangle of it, but not colours, textures or materials. The page says when the file had them. For printing and CAD that is what matters; for a textured game asset, keep the GLB.
Why is my glTF so small or lying on its side?
glTF measures in metres and stands models on the Y axis; STL and slicers use millimetres and the Z axis. This converter turns and scales between them, and "Keep axes and units as they are" turns that off.
Can it convert STEP or IGES?
Yes, into any of the mesh formats: drop the .step, .stp, .iges or .igs file and OpenCASCADE cuts its solids into triangles in your browser. The other way, a mesh is saved as a STEP solid made of flat faces (see the STL to STEP converter).
What about compressed glTF?
Draco and meshopt compressed glTF files are recognised and reported; export them again without mesh compression to convert them here.