Convert STP to STL
Free STP to STL converter that runs in your browser. See real dimensions before you download, and get a watertight, slicer-ready file.
Why convert STP to STL?
An .stp file is exactly the same format as .step; the shorter extension comes from older systems that limited names to three letters. The reason to convert it is also the same: slicers and most mesh tools cannot open exact CAD solids, so STP has to become an STL before printing. If you downloaded a part from a manufacturer's catalogue, a McMaster-style parts library or a colleague's CAD export, the file is probably an STP with exact surfaces. MeshShift reads it in your browser with OpenCascade and tessellates it into triangles at a quality you choose. The file stays on your device, and the unit stored inside the STP decides the final size.
How to convert STP to STL
- Drop your STP file onto the converter — it opens in your browser, nothing is uploaded.
- Check the preview and the dimensions in mm; fix units or the up axis in “Units & orientation” if the size or orientation looks wrong.
- Choose STL as the output (binary is smaller; ASCII is human-readable) and click Convert. Several files download as one ZIP.
What carries over from STP to STL
| STP | STL | Result | |
|---|---|---|---|
| Colour / materials | Yes | No | Dropped |
| Textures | No | No | — |
| Units stored in file | Yes | No | Numbers in mm |
| Separate parts | Yes | No | Merged into one mesh |
| Usual up axis | Z | Z | Unchanged |
What changes
- Exact surfaces are approximated by triangles, so very fine curves depend on the quality setting.
- The assembly structure and part names are lost; everything becomes one mesh.
- Colours and material labels in the STP are not carried into STL.
- Product data such as part numbers and notes stored in the STP are dropped.
Tips
- If the part looks tiny or giant in your slicer, compare the dimensions shown here with the catalogue drawing.
- Use Fine quality for threaded parts or small radii; Normal is fine for brackets and enclosures.
- Catalogue assemblies often include screws and internal parts you do not want to print; check the part count in the viewer first.
- Run the free print check if the model came from a scan-to-CAD workflow.
About STP files
STEP, formally ISO 10303 and known as the Standard for the Exchange of Product model data, has been developed since the 1980s and is the main neutral format for moving CAD models between companies and systems. The usual application protocols are AP203 and AP214 for geometry and assemblies, and AP242 for modern product and manufacturing information. A .step or .stp file is plain text written in the EXPRESS-based Part 21 syntax. Unlike STL, it does not store triangles: it stores boundary representation (B-rep) geometry, meaning exact planes, cylinders, splines and NURBS surfaces joined by edges and faces into solids. That keeps holes perfectly round and dimensions precise, and allows the receiving CAD to keep editing faces. Files can contain assemblies, product structure, colours and units.
About STL files
STL was created by 3D Systems in the late 1980s for its stereolithography machines, and it became the default exchange format for 3D printing. A file describes a surface as a list of triangles, each with three vertices and a facet normal. That is all it contains. There is no header field for units, no colour, no texture and no notion of separate parts. Two flavours exist: ASCII, which is readable text but large, and binary, which spends exactly 50 bytes per triangle after an 80-byte header and a 4-byte triangle count. Binary is what almost every modern tool writes. Because the format is so small and so old, every slicer, CAD package and mesh editor can read it, which is why hobbyists still download most printable models as STL from sites like Printables and Thingiverse.
3D printing notes
STL is still the safest file to hand to a slicer. Bambu Studio, PrusaSlicer, OrcaSlicer, Cura and the resin tools Chitubox and Lychee all import it, and they all treat the numbers as millimetres. The usual problems are scale (a model exported from a metre-based tool arrives 1000 times too small) and meshes that are not watertight, which makes slicers fill or skip regions. MeshShift shows the real dimensions before you convert and can scale from metres automatically. Its print check lists holes, non-manifold edges and flipped normals, and one click rebuilds a closed solid at the same size. If you need colours or several plates in one file, use 3MF instead.
Frequently asked questions
Is STP the same as STEP?
Yes. STP and STEP are the same ISO 10303 format with two common extensions. Both are read the same way and converted to STL with the same tessellation settings.
Can I print an STP directly?
Not with common slicers. They need a triangle mesh such as STL or 3MF, so convert first. Keep the original STP if you may need to edit the design later.
Is this STP to STL converter free and private?
Yes. The conversion runs in your browser with JavaScript and WebAssembly, so your STP file is never uploaded to a server. There is no sign-up, no watermark and no daily limit; very large files are limited only by your device's memory.