Free Online Converter
Convert STEP to STL
Drop a .step or .stp file and download a clean STL in seconds. Reads CAD solids with OpenCASCADE and tessellates them for any slicer. Runs entirely in your browser — no upload, no signup, no watermark.
How to convert STEP to STL
- Drag your
.stepfile into the box above (or click to browse). - Preview the model in the viewer — drag to rotate, scroll to zoom.
- Click Convert & Download .stl. The
.stlfile lands in your downloads folder.
Conversion runs in your browser via three.js. Your file never leaves your device — there's no upload, no server, and nothing is stored.
Converting a STEP / STP file to STL
STEP (.step or .stp — same ISO 10303 format, two extensions) is a precise B-rep CAD format that stores exact analytic surfaces and solids. STL is a triangle-mesh approximation of those surfaces. This converter reads your STEP with OpenCASCADE compiled to WebAssembly and tessellates the solid into a standard STL that any slicer or mesh tool accepts.
Both .stp and .step work here — they're the same thing. Curved faces become many small triangles in the STL, so a round hole turns into a faceted ring rather than a true cylinder. That's expected: STL has no concept of analytic geometry, only triangles.
There's no STL-to-STEP here on purpose. Once a model is a mesh, the exact CAD surfaces are gone, so it can't be rebuilt into an editable solid. Anything that claims to convert STL back to STEP is just wrapping the triangles in a STEP shell — it opens in CAD but isn't a real parametric part.
Frequently asked questions
How do I convert a STEP file to STL?+
Drop your .step or .stp file into the box above, preview it in the 3D viewer, then click Convert & Download .stl. It's read and tessellated entirely in your browser — nothing is uploaded.
Is STP the same as STEP?+
Yes. .stp and .step are just two extensions for the same ISO 10303 CAD format. This converter accepts both.
Is the STEP to STL converter free?+
Yes. It's free with no signup, no watermark, and no file-size paywall. Flip3D runs the OpenCASCADE engine locally in your browser.
What quality is the converted mesh?+
The CAD solid is tessellated automatically into a detailed triangle mesh that's suitable for slicing and 3D printing. STL is an approximation of the exact STEP surfaces, so very tight curves become many small facets.
Is my STEP file uploaded anywhere?+
No. There is no upload and no server. The WebAssembly OpenCASCADE reader runs on your device, and nothing is stored.
Can I convert STL back to STEP?+
No, and we won't pretend to. STL is a triangle mesh, and a mesh can't be turned back into an editable CAD solid — the exact surfaces are gone once a model is tessellated. Tools that output a "STEP" from an STL just wrap the triangles in a STEP shell; it opens but isn't a real parametric part.