How to convert STL to STP
- Drop your .stl file into the box above, or click Choose file.
- Check the 3D preview, size and triangle count.
- Make sure STP is selected as the output format. Adjust scale or up-axis if needed.
- Click Download. The .stp file is created instantly on your device.
Why convert STL to STP?
Engineers often receive an STL but need a STEP to place the part in a CAD assembly, check clearances or design a fixture around it. This converter writes every triangle as a flat face of a faceted solid, which SolidWorks, Fusion, Inventor, Onshape and FreeCAD import as a body.
What changes in the conversion
- Triangles become flat faces. STP is a CAD format, but a mesh has no parametric surfaces. The result is a faceted solid you can measure and combine, not a smooth editable feature tree.
- Geometry is preserved. Every triangle, with all object transforms applied, ends up in the new file.
STL vs STP
| STL | STP | |
|---|---|---|
| Full name | Stereolithography | ISO 10303 (STEP AP203/AP214/AP242) |
| Stores | geometry only | exact solids, assemblies and part names |
| Colour | No | Yes |
| Textures | No | No |
| Units | none – most programs read STL numbers as millimetres | stored in the file (usually millimetres) |
| Exact CAD geometry | No | Yes |
About the formats
STL (Stereolithography) was created by 3D Systems in 1987 for its stereolithography printers. It describes only the surface of a model as a list of triangles, without colour, materials or units. It is the default file for 3D printing and the format almost every slicer (Cura, PrusaSlicer, Bambu Studio, Chitubox) opens.
STP (ISO 10303 (STEP AP203/AP214/AP242)) was standardised as ISO 10303 for exchanging engineering data between CAD systems. It describes exact solid geometry (B-rep surfaces, edges and assemblies) rather than triangles. It is the neutral CAD format used by SolidWorks, Fusion 360, Inventor, CATIA, FreeCAD and Onshape. ".stp" and ".step" are two extensions for exactly the same ISO 10303 format.
Frequently asked questions
Is this converter free?
Yes. You can convert STL to STP for free – up to 3 conversions a day, with no sign-up and no watermark. If you need more, Pro gives you unlimited conversions and batch conversion (free for 7 days).
Are my files uploaded to a server?
No. The conversion runs entirely in your browser using WebAssembly and JavaScript. Your model never leaves your computer, which also makes it safe for confidential parts and patient data.
Is there a file size limit?
There is no fixed limit. Files of a few hundred megabytes work on a typical laptop; the practical limit is your device's memory.
Can I edit the STEP file like a normal CAD model?
You can measure it, move it, cut it and use it in assemblies and Boolean operations. Because it is made of many flat faces, you will not get editable sketches or smooth cylinders – that would require reverse engineering. For heavy meshes, reduce the triangle count first (e.g. in Meshmixer or Blender) so the CAD program stays responsive.
Will the part be a solid or a surface?
If the STL is watertight (every edge shared by two triangles) the STEP contains a closed faceted solid. If the mesh has holes, it is written as an open shell (surface body), which CAD programs can still display and measure.