How to convert STL to 3MF
- Drop your .stl file into the box above, or click Choose file.
- Check the 3D preview, size and triangle count.
- Make sure 3MF is selected as the output format. Adjust scale or up-axis if needed.
- Click Download. The .3mf file is created instantly on your device.
Why convert STL to 3MF?
3MF stores units explicitly, compresses well (often 3–5× smaller than binary STL) and is the native project format of modern slicers. Converting STL to 3MF makes files smaller to share and removes any doubt about whether a model is in millimetres or inches.
What changes in the conversion
- Geometry is preserved. Every triangle, with all object transforms applied, ends up in the new file.
STL vs 3MF
| STL | 3MF | |
|---|---|---|
| Full name | Stereolithography | 3D Manufacturing Format |
| Stores | geometry only | geometry, units, colours and (slicer-specific) print settings |
| 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 | No |
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.
3MF (3D Manufacturing Format) was developed by the 3MF Consortium (Microsoft, HP, Autodesk, Ultimaker and others) since 2015. It is a zipped XML package that stores meshes together with units, colours, materials and print settings. It is the modern replacement for STL in 3D printing – PrusaSlicer, Bambu Studio and Cura save projects as 3MF.
Frequently asked questions
Is this converter free?
Yes. You can convert STL to 3MF 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.