Convert OBJ to STL Online — Free 3D Printing Ready

Convert your OBJ 3D models to STL format for 3D printing. OBJ is a universal 3D modeling format used by Blender, Maya, 3ds Max, and most digital content creation (DCC) tools. STL is the de facto standard for 3D printing, supported by all slicing software like Cura, PrusaSlicer, and Simplify3D.

Our browser-based converter processes your files locally using WebAssembly — no upload, no privacy risk, no server delays. Supports large files up to 50MB on desktop. Conversion completes in seconds for typical models.

Perfect for the Blender-to-3D-printer workflow: export your model as OBJ, convert to STL, then import to your slicer software.

Drag OBJ file here, or click to upload

Supports .obj files up to 50MB

Technical Details

What Changes During Conversion

Converting from OBJ to STL involves significant information loss because STL is a minimal geometry-only format. Geometry (vertex positions and faces) is preserved, but polygon faces are triangulated. Materials, textures, UV coordinates, and vertex colors are all discarded. Normals are recalculated as per-face normals (flat shading). This converter outputs Binary STL by default, which is 50-90% smaller than ASCII STL.

3D Printing Considerations

OBJ files may not have explicit unit definitions. Most slicers assume STL is in millimeters. If your model appears too large or too small, scale in your slicer. 3D printers require watertight meshes -- no holes, no inverted normals, no self-intersecting geometry. If your OBJ has non-manifold geometry, use Blender's 3D Print Toolbox, Meshmixer, or Netfabb to repair.

Common Use Cases

Blender to 3D Printer Workflow

The most common use case. Export your Blender model as OBJ, convert to STL, then import to Cura, PrusaSlicer, or Simplify3D for slicing.

Repairing Downloaded Models

Downloaded a model from TurboSquid, CGTrader, or Sketchfab as OBJ? Convert to STL to prepare for 3D printing.

CAD to 3D Printing

Some CAD tools export OBJ but not STL. Use this converter to complete the CAD-to-print pipeline.

OBJ vs STL: Quick Comparison

FeatureOBJSTL
GeometryPolygons (quads, n-gons)Triangles only
MaterialsSupported (.mtl file)Not supported
TexturesSupported (UV coords)Not supported
File TypeText (.obj)Text (ASCII) or Binary
Primary UseModeling, interchange3D printing
EditingExcellent (keeps n-gons)Poor (triangulated)

Use OBJ for modeling, editing, rendering, and archiving. Use STL as the final step before 3D printing.

Frequently Asked Questions

No. STL is a geometry-only format. Colors, materials (from .mtl files), and textures are discarded during conversion. The output STL will be a gray mesh. If you need colored 3D prints, export vertex colors from Blender and use a multi-material printer with a slicer that supports color STL extensions (non-standard).
Usually, yes -- but you should always check the mesh in your slicer first. If the original OBJ has non-manifold geometry (holes, inverted normals, intersecting faces), the STL will inherit those issues. Use your slicer's repair tools (Cura, PrusaSlicer Fix through Netfabb) or Meshmixer's Inspector.
Binary STL is smaller (50-90% smaller) and faster to process. ASCII STL is human-readable text. This converter outputs Binary STL by default, which is what most modern slicers prefer.
STL files are typically 50-100% larger than OBJ (for the same geometry) because STL stores face normals and uses less efficient vertex indexing. A 10 MB OBJ might become a 15-20 MB Binary STL.
Not in MVP. This converter processes the .obj file only. Materials and textures are discarded (STL doesn't support them anyway). Multi-file uploads are planned for Phase 2.

Related Converters

STL to OBJ Converter

Need to edit your STL files? Convert STL back to OBJ for Blender, Maya, or other DCC tools.

OBJ to GLB Converter

Want to display your model on the web? Convert OBJ to GLB for Web3D rendering.