Free Online OBJ to STL Converter
OBJ is what modelling tools hand you; STL is what slicers demand. This converter bridges the two and drops everything a printer cannot use — materials, UVs and colour — while keeping the geometry intact.
Because STL stores an unindexed triangle soup, expect the file to grow. A 20 MB OBJ commonly lands between 40 MB and 90 MB as binary STL; that is normal, not a bug.
Upload your OBJ file
Select one model together with its MTL, BIN and texture files. Resource filenames must be unique; the combined size must fit the upload limit. For missing resources, package the model as GLB in its source application.
Scale factor. Leave empty to keep the original size.
Preview in 3D
How to convert OBJ to STL
Select your OBJ file
Choose one model and its companion material, buffer and image files when applicable. The combined upload limit is 50 MB.
Check the preview and options
Check orientation, dimensions and required resources. Image reliefs are previewed after conversion; set their width and depth first.
Convert and download STL
Convert, then inspect the result and any warnings. Textured OBJ results download as a ZIP containing the OBJ, MTL and textures.
Why choose this converter
Real mesh conversion
Geometry is parsed and exported into the destination format.
Inspect the result
Use the preview, output statistics and format warnings to check the conversion.
Server conversion
A server mesh pipeline converts geometry. OBJ resources are returned together in a ZIP.
Static model scope
Animations, rigs, CAD construction history and unsupported material extensions are outside this converter's scope.
What changes in this conversion
- Texture maps and UVs will be dropped.
- Material definitions will be dropped.
- Colour information will be dropped.
- Quad / n-gon topology will be dropped.
What Is a OBJ File? / STL
OBJ
OBJ is a plain-text geometry format from Wavefront. It stores vertex positions, texture coordinates, normals and faces, and references a companion .mtl file for materials and texture maps. Because it is text, it is human-readable and trivially editable, but also noticeably larger than binary alternatives.
- Readable and editable as text
- Supports materials and texture maps via MTL
- Broad support in DCC tools
- Needs the .mtl and texture files to look right
- Large file size for dense meshes
- No animation, no units, no scene graph
STL
STL stores a raw triangle soup: three vertices per facet plus a normal. There is no index buffer, no colour, no material and no unit. Because the format is so minimal, virtually every slicer, printer and CAD tool reads it, which is exactly why it is still the default handoff for 3D printing.
- Universally supported by slicers and printers
- Dead simple to parse and stream
- Binary variant keeps file size predictable
- No colour, texture or material information
- Duplicated vertices inflate file size
- No unit or scene hierarchy
OBJ vs STL
| Property | OBJ | STL |
|---|---|---|
| Encoding | text | binary or ASCII |
| Colour | Yes | No |
| Texture maps | Yes | No |
| Materials | Yes | No |
| Animation | No | No |
| Units | No | No |
| Best for 3D printing | Yes | Yes |
| Best for the web | No | No |
| Best for game engines | Yes | No |
Before you convert
- Close the mesh first — slicers reject open shells.
- Apply all modifiers so the exported OBJ matches what you see.
- Set real-world units before exporting; STL itself carries none.
Common problems
The STL is far larger than the OBJ
Export binary STL instead of ASCII, and decimate dense scan meshes before converting.
The slicer reports non-manifold edges or holes
Repair the mesh in the STL editor — fill holes, merge duplicate vertices and fix normals — then re-convert.
It prints at the wrong scale
STL has no unit. Measure the bounding box after converting and scale to your target size in millimetres.
Colours and textures are gone
That is inherent to STL. Convert to 3MF instead if you need colour to survive.
Frequently Asked Questions
Can I convert OBJ to STL here?
Yes. Select the file and any companion resources, check the preview, then convert and download.
Is an account or payment needed?
No. Available conversions are free and do not require an account.
What is the file size limit?
50 MB combined, with at most one model and 63 companion files.
Will materials and textures survive?
This conversion exports geometry. STL and this service's 3MF writer do not retain materials or textures; PLY may retain vertex colors. Use GLB when materials are required.
Are animation and rigs preserved?
No animation or rig preservation is promised. Browser conversions export static meshes; check proprietary material features and real-world scale in the result.
Are uploaded models published?
No. Conversion does not add models to the public gallery. Browser USDZ export stays local; server conversions use temporary download files.