Browser-local converter
STL to OBJ converter
Convert an STL into a Wavefront OBJ locally. Both ASCII and binary STL are read, and the resulting OBJ is checked by parsing it back and comparing the geometry.
Drop your STL files here
STL, OBJ, PLY, GLB, glTF, 3MF and SVG. Nothing is uploaded: files are read and converted inside this tab. Checking what this device can handle...
Queue
No files yet. Drop models above, or use the file picker.
Output
Units
Size and placement
Repair and cleanup
These can change the shape, so they need a before-and-after review before export.
Inspection
Add a model to see its dimensions, mesh health and estimated volume.
What this STL to OBJ conversion does and does not do
- STL is a flat soup of triangles with no shared vertices, so a converted OBJ has three separate vertices per triangle unless you weld first. Welding is offered in the workspace, with the tolerance shown.
- Neither format records a unit, so the coordinates are copied across unchanged.
- STL has no materials, so the OBJ is written without a material library unless you add materials in the workspace.
- STL has no texture coordinates, so the OBJ has none either. No uv unwrapping is performed: generating a uv layout is a modelling decision, not a conversion.
- Per-facet colour from vendor-specific STL extensions is not read, because it is not part of the STL format.
Troubleshooting
The OBJ has far more vertices than I expected
That is STL doing its job badly. Every triangle carries its own three vertices. Run weld with the suggested tolerance before exporting and the vertex count usually drops by around two thirds.
The surface looks faceted in my 3D application
STL stores no smooth normals. Use recalculate normals with smoothing before exporting, and the OBJ will carry per-vertex normals.
The file is very large
OBJ is a text format and is naturally bigger than binary STL. Welding vertices first makes the largest difference.
Questions
Does converting STL to OBJ improve the model?
Not by itself. It is the same triangles in a different container. What does help is welding duplicate vertices and recalculating normals, both of which the workspace can do and both of which report exactly what they changed.
Can I get a solid or NURBS model out of this?
No. An STL is a mesh of flat triangles, and the original curves and features are simply not in the file. Any tool claiming to recover true NURBS surfaces from a mesh is fitting new geometry, not recovering yours.
Will the OBJ open in Blender and Maya?
Yes. The OBJ is written to the standard, and every export is validated by re-parsing it and comparing triangle counts and bounds before you download it.