Convert OBJ to STL Online (Free & Secure)
To convert OBJ to STL, drop your .obj file on this page and download a .stl file seconds later. The route is OBJ → GLB → STL (parsed into a GLB scene, then exported as STL), and textures are dropped because STL cannot hold them.
Select .OBJ file
or drag & drop .obj file here
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⚡ AI Summary & Quick Answer
To convert OBJ to STL, drop your .obj file on this page and download a .stl file seconds later. The route is OBJ → GLB → STL (parsed into a GLB scene, then exported as STL), and textures are dropped because STL cannot hold them.
Modelling and animation formats carry far more data than a printer needs, so the converter keeps the surface and drops everything else. OBJ (.obj) is plain ASCII text with a companion .mtl material file. It holds polygons (triangles, quads and n-gons) with shared UV and normal pools and is most often opened in Blender, Maya, and 3ds Max. STL (.stl) is a binary (or ASCII) list of unindexed triangles, holding raw triangle facets without shared vertices or UV coordinates, and is typically used in Cura, PrusaSlicer, and Bambu Studio.
Under the hood, the OBJ file is decoded into an in-memory scene, then serialised as STL. The axis convention moves from conventionally Y-up, but not enforced to Z-up, matching 3D printer coordinates. Everything runs in your browser or an isolated, auto-purged instance, so models stay private.
.objAbout OBJ (Wavefront)
Universal geometry definition format supported by almost every 3D modeling and rendering software.
- Structure: plain ASCII text with a companion .mtl material file
- Materials: Phong-style MTL materials (diffuse, specular, ambient)
- Units: unitless (the importing application decides the scale)
- Axis: conventionally Y-up, but not enforced
- Opens in: Blender, Maya, 3ds Max, ZBrush or MeshLab
.stlTarget format: STL (Stereolithography)
The standard format for 3D printing and additive manufacturing. Defines surface geometry using unstructured triangulated facets.
- Structure: a binary (or ASCII) list of unindexed triangles
- Materials: no material information
- Units: unitless (slicers usually assume millimeters)
- Axis: Z-up, matching 3D printer coordinates
- Opens in: Cura, PrusaSlicer, Bambu Studio, Fusion 360 or MeshLab
What happens to your data in OBJ → STL conversion
Conversion route: OBJ → GLB → STL (parsed into a GLB scene, then exported as STL).
| Aspect | Result | Outcome |
|---|---|---|
| Geometry | Preserved | OBJ stores polygons (triangles, quads and n-gons) with shared UV and normal pools; STL stores raw triangle facets without shared vertices or UV coordinates. Surfaces are retriangulated where needed and positions, normals and UV coordinates are carried across. |
| Materials | Not supported | OBJ uses Phong-style MTL materials (diffuse, specular, ambient), but STL has no material information; material settings cannot be stored in the output. |
| Textures | Not supported | In OBJ, texture images are referenced by file name from the MTL file. STL has no texture support, so images are dropped and only geometry remains. |
| Vertex colours | Not supported | STL cannot store vertex colours, so colour that lives in OBJ vertices is lost unless it is baked into a texture first. |
| Animation | Not applicable | OBJ is a static format, so the STL result is a single static pose. |
| Units & scale | Adapted | OBJ uses unitless (the importing application decides the scale); STL uses unitless (slicers usually assume millimeters). Check the scale in your target application, and use the Scale tool if the model looks too big or too small. |
| Orientation | Adapted | OBJ is conventionally Y-up, but not enforced and STL is Z-up, matching 3D printer coordinates. The converter writes a consistent orientation, but verify the up axis in your target software. |
Expect the STL file to be roughly 1.6x smaller than the OBJ source, since STL is about 50 bytes per triangle in binary form, so large for dense meshes.
Why convert OBJ to STL?
Why leave OBJ
People most often convert from OBJ when they are rescuing an old sculpt or archive from a text-based format. Other common cases include moving a model out of ZBrush or Blender into a web pipeline and turning a vendor download into a modern, textured asset. In OBJ → STL specifically, preserved: geometry; adapted: units & scale and orientation; not supported by STL: materials, textures, and vertex colours. Expect the STL file to be roughly 1.6x smaller than the OBJ source, since STL is about 50 bytes per triangle in binary form, so large for dense meshes.
Why choose STL
STL is the right target when you are sending geometry to CNC and rapid-prototyping software. It also fits scenarios such as preparing a model for FDM or resin printing and producing a minimal mesh with no extra data. Modelling and animation formats carry far more data than a printer needs, so the converter keeps the surface and drops everything else.
Where the result opens
After conversion you can open the .stl file in Cura, PrusaSlicer, Bambu Studio, Fusion 360 or MeshLab.
Step-by-Step Guide: OBJ → STL
- 1
Upload your .obj file
Drag your OBJ model onto the converter or click to browse. Texture images are referenced by file name from the MTL file; zip the model with its textures and companion files if you want them included.
- 2
Check your free quota
Free accounts can run a few conversions per day; signing in unlocks tracking of your remaining uses. No watermark is ever added.
- 3
Convert to STL
Press the Convert to STL button. The pipeline follows OBJ → GLB → STL (parsed into a GLB scene, then exported as STL), which usually takes a few seconds for models under 100 MB.
- 4
Download the .stl file
Your STL file downloads automatically. Open it in Cura and PrusaSlicer to confirm scale and orientation.
Tips for OBJ → STL
- No unit information means scale surprises between applications (OBJ source).
- Non-manifold edges and holes make slicers fail (STL target).
- If colour matters, bake it into a texture before exporting to STL, or choose a format that keeps it such as GLB.
- Always verify real-world size: OBJ is unitless (the importing application decides the scale), while STL is unitless (slicers usually assume millimeters).
Frequently Asked Questions
How do I convert OBJ to STL without losing quality?
Upload the .obj file and press convert; the route is OBJ → GLB → STL (parsed into a GLB scene, then exported as STL). Geometry is carried over exactly; materials are mapped to the closest STL equivalent, and textures are not stored in STL.
Does OBJ to STL conversion keep textures?
In OBJ, texture images are referenced by file name from the MTL file. STL has no texture support, so images are dropped and only geometry remains.
Why does my STL model look the wrong size or rotation?
OBJ uses unitless (the importing application decides the scale); STL uses unitless (slicers usually assume millimeters). Check the scale in your target application, and use the Scale tool if the model looks too big or too small. OBJ is conventionally Y-up, but not enforced and STL is Z-up, matching 3D printer coordinates. The converter writes a consistent orientation, but verify the up axis in your target software.
Will the STL file be bigger or smaller than my OBJ file?
Expect the STL file to be roughly 1.6x smaller than the OBJ source, since STL is about 50 bytes per triangle in binary form, so large for dense meshes.
What software can open the converted STL file?
STL files open in Cura, PrusaSlicer, Bambu Studio, Fusion 360 or MeshLab. If you need to go back, use the STL to OBJ converter.
Is it safe to upload my OBJ model?
Yes. Files are processed in your browser or on isolated instances and purged right after conversion. They are never used to train AI models, and no watermark is added.