Convert STEP or STP to STL Online
Check the part free, then download a watertight STL in millimetres
To convert a .step or .stp file to STL, drop it on the viewer below and check the part free in your browser, with nothing to install. Then open it in Studio and download a watertight STL in millimetres for 1 credit.
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.
Is an STP file the same as a STEP file?
Yes. .stp and .step are two extensions for the same format, ISO 10303 (STEP). The three-letter .stp dates from systems that allowed only three-character extensions, and many programs still write it. Both hold the same exact solid, so an STP file converts to STL exactly like a STEP file, with no renaming.
A STEP file stores exact geometry: real curved surfaces described mathematically. An STL stores a triangle mesh, the same shape approximated by thousands of flat facets. Every slicer and 3D printer reads STL. Going from the exact solid to a mesh is the easy, standard direction, and because the solid is closed, the STL comes out watertight and manifold.
How do I convert STEP to STL online?
Upload the .step or .stp file to the viewer at the top of this page, check the part in the free 3D view, then open it in Studio and download it as STL. Nothing installs on your computer, and the one credit is charged only when you download.
- 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: rotate and zoom to confirm it is the right model before you spend anything.
- Download as STL: open the model in Studio, click Download and choose STL (or 3MF). Exporting the mesh costs 1 credit.
How do I convert STEP to STL in a CAD program?
Open or import the STEP file, then export or save the body as STL. Every mainstream CAD program does this in a few clicks; the only setting that matters is the mesh resolution, covered below. If you have no CAD program installed, the online route above is quicker.
- FreeCAD: open the STEP, select the solid in the tree, then File → Export and choose STL Mesh.
- Fusion: right-click the body in the browser and choose Save As Mesh, with STL as the format.
- SolidWorks: open the STEP, then File → Save As and pick STL; Options sets the resolution.
- Onshape: import the STEP, right-click the part and choose Export, with STL as the format.
What STL resolution should I use?
Use a mesh fine enough that you cannot see facets on printed curves, and no finer. More triangles hug cylinders and fillets more closely but make bigger files that slice slower. Studio picks the resolution from the size of your part, so small holes stay round without bloating large parts.
In a CAD program the setting is usually called deviation (or chord height) plus an angle. A deviation of a few hundredths of a millimetre is plenty for most printing. With FDM, layer height and nozzle size limit detail long before a sensible STL resolution does, so you rarely need the finest export.
Why is my STL the wrong size?
Because STL stores no units. A STEP file records whether it is in inches or millimetres; an STL is just numbers, and slicers read them as millimetres. A part exported in inches therefore shows up 25.4 times too small. The STL from Studio is written in millimetres, so it opens at the right size.
If an STL from somewhere else arrives tiny, it was almost certainly exported in inches: scale it by 2540% in the slicer to turn inches into millimetres.
Should I keep the STEP file after converting?
Yes. The STL is a printable mesh, but it no longer holds editable solid geometry. If the part might change later, such as a new hole, a different dimension or a machined version, keep the original STEP. A machine shop will ask for it, and edits start from it rather than from a mesh.
In the STEP viewer the model stays live after import, so you can ask for a change in plain English and export a fresh STL.
Can I put this converter on my own site?
Yes. Run a marketplace, a parts catalog or a docs site? Drop this exact viewer on any page with one line, and visitors view and convert CAD files without leaving your site. It is free and customizable.
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<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.
Frequently asked questions
How do I convert a STEP file to STL?
Upload the .step or .stp file to the viewer at the top of this page. It renders free so you can check the part. Then open it in Studio, click Download and choose STL. The download costs one credit.
How do I convert STP to STL?
The same way. STP is just the short extension for a STEP file, so a .stp file uploads, previews and converts exactly like a .step file. You do not need to rename it first.
Is STEP to STL free?
Uploading and viewing your STEP file are free and run in your browser with nothing to install. Downloading the converted STL happens in Studio and costs one credit per download.
Will the STL be watertight and printable?
Yes. A STEP file describes a closed solid, so the STL made from it is a watertight, manifold mesh, the clean input a slicer wants. Print quality then depends on mesh resolution and your slicer settings, not on the conversion.
What units is the STL in?
Millimetres. An STL file stores no units at all, so slicers assume millimetres. The STL you download from Studio is written in millimetres, so it opens at the right size even if the part was designed in inches.
STEP vs STL: which do I need?
Send STEP to a machine shop or when the part will be edited further: it stores exact surfaces. Send STL to a 3D printer or slicer: it is a triangle mesh approximation. If you have a STEP file and need to print it, converting to STL is the right step.
Can I convert STL back to STEP?
Yes, with a catch. Our STL to STEP converter stitches the mesh into a solid and merges flat regions into true planar faces, so blocky parts come out clean. Curved surfaces stay as small flat facets, because the mesh never recorded exact curves. If you need exact curves, keep the original STEP.
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, such as DWG or a native .sldprt file. Re-export it as STEP from the program that created it and it will open.
What if I only have a drawing, not a STEP file?
Then there is nothing to convert yet. Our Drawing to STEP service turns a PDF, PNG or JPG into a STEP model in minutes: $9.99 to build it, files from $29.99, and you can make the STL from that STEP here.