Convert STEP to STL Online
Turn a .step or .stp file into a printable STL mesh. Upload your file and view it free in the browser to confirm it is the right part, then download the converted STL in Studio (1 credit). Runs in the browser, nothing to install.
Drag a .step / .stp file onto the viewer above (or tap Upload) — it renders right here, free, nothing to install. To get the STL, open it in Studio and hit Download — exporting the STL costs 1 credit.
STEP → STL, the clean direction
A STEP file (ISO 10303) stores exact geometry — real curved surfaces described mathematically. An STL file stores a triangle mesh: the same shape approximated by thousands of flat facets. Every slicer and 3D printer speaks STL.
Converting STEP to STL is the easy, standard direction. You start from an exact solid and sample its surfaces into triangles — a well-defined, lossless-enough operation that every CAD package performs the same way. Because the STEP model is already a closed solid, the resulting STL is watertight and manifold: exactly the clean input a slicer expects.
The reverse — STL back to STEP — is a different problem entirely. Rebuilding exact surfaces from a bag of triangles is hard reverse engineering, and no tool does it reliably from an arbitrary mesh. If you only have an STL, you can view and inspect it here, but plan to remodel rather than auto-convert. Convert STEP to STL while you still have the STEP.
How to convert
- Upload your .step or .stp file to the viewer above (drag and drop, or tap Upload). Files up to 75 MB are supported.
- View it free — the part renders in the 3D view so you can rotate, zoom, and confirm it is the right model before you spend anything.
- Download as STL — open the model in Studio and click Download, then choose STL. Exporting the mesh costs 1 credit.
Nothing installs on your machine — the whole flow runs in the browser. Viewing and uploading are free; the single credit is charged only when you download the converted file.
Choosing STL resolution / quality
An STL approximates curves with flat triangles, so resolution is a trade-off between fidelity and file size:
- Higher resolution — more triangles hug curved surfaces tightly, so cylinders and fillets look smooth. Larger files, slower slicing. Best for visible, curved, or precision parts.
- Lower resolution — fewer triangles, smaller files, faster to slice. Fine for blocky or purely functional parts where facet lines will not matter.
A good default is a mesh fine enough that you cannot see facets on the printed curves. For FDM printing, layer height and nozzle size usually limit quality well before a reasonable STL resolution does — so you rarely need the absolute finest export.
Keep the STEP too
Once you have exported an STL you have a printable mesh, but you no longer have editable solid geometry in that file. If the part might change later — a new hole, a different dimension, a machined version — keep the original STEP around. With the STEP viewer the model stays live after import, so you can ask for a change in plain English and re-export, rather than starting over from a mesh.
Put this converter on your site
Run a marketplace, a parts catalog, or a docs site? Drop this exact viewer on any page with one line — visitors view (and convert) CAD files without leaving your site. Free, and customizable.
<script src="https://cdn.partwork.ai/viewer/partwork_viewer_widget.js" defer></script>
<div data-partwork-viewer data-theme="dark" style="width:100%;height:520px"></div>See colors, fonts, fixed-model, and viewer-only options on the embed page.
Common questions
How do I convert a STEP file to STL?
Upload the .step or .stp file to the viewer above — it renders free so you can check the part. Then open it in Studio, click Download, and choose STL. The download costs one credit.
Is STEP to STL free?
Uploading and viewing are free and run in your browser. Downloading the converted STL costs one credit. We do not gate the view behind an install or a payment — you only spend when you take the file.
Will the STL be watertight and printable?
Yes. A STEP file is a closed solid, so the STL exported from it is watertight and manifold — the clean input a slicer wants. Print quality then comes down to mesh resolution and your slicer settings.
STEP vs STL — which do I need?
Send STEP to a machine shop or when the part will be edited further; send STL to a slicer or 3D printer. See STL vs STEP for the full comparison.
Can I convert STL back to STEP?
Not cleanly. STEP → STL throws away precision to make triangles, which is easy. Rebuilding exact surfaces from a mesh is hard reverse engineering that no tool does reliably from an arbitrary STL. You can view an STL here, but expect to remodel if you genuinely need a solid.
What if my file will not upload?
Most often it is over the 75 MB limit, or it is a format we do not read (notably DWG or native files like .sldprt). Re-export as STEP from whatever created it and it will open.
Convert your file
Upload your .step or .stp file above, confirm the part in the free 3D view, then download the converted STL in Studio (1 credit). In the browser, nothing to install.