How to convert STP to STL
- Drop your .stp file into the box above, or click Choose file.
- Check the 3D preview, size and triangle count.
- Make sure STL is selected as the output format. Adjust scale or up-axis if needed.
- Click Download. The .stl file is created instantly on your device.
Why convert STP to STL?
Slicers and many mesh tools cannot read CAD files. Converting STEP to STL tessellates the exact CAD surfaces into triangles so you can 3D print the part, render it, or share it with someone who has no CAD software.
What changes in the conversion
- Surfaces become triangles. STP stores exact curved surfaces; STL stores a triangle mesh. Curves are approximated with a fine tolerance.
- Colours are dropped. STL only stores geometry.
- Geometry is preserved. Every triangle, with all object transforms applied, ends up in the new file.
STP vs STL
| STP | STL | |
|---|---|---|
| Full name | ISO 10303 (STEP AP203/AP214/AP242) | Stereolithography |
| Stores | exact solids, assemblies and part names | geometry only |
| Colour | Yes | No |
| Textures | No | No |
| Units | stored in the file (usually millimetres) | none – most programs read STL numbers as millimetres |
| Exact CAD geometry | Yes | No |
About the formats
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.
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.
Frequently asked questions
Is this converter free?
Yes. You can convert STP to STL 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.
How accurate is the triangulation?
Curved surfaces are approximated with a fine tolerance suitable for 3D printing. Flat faces stay exact. The STL is written in millimetres, using the units stored in the STEP file.
Does it work with assemblies?
Yes. All bodies of an assembly are converted; they are exported together into one STL. Use 3MF or GLB if you want to keep them as separate objects.