OBJ to STL Converter
Get a model out of Blender, ZBrush, a photogrammetry app or a game asset pack and into a 3D printer's workflow. The converter triangulates the OBJ, drops what printers cannot use and writes a compact binary STL.
3D Model Converter
or drop STL, OBJ, MTL … files here ·
Max 95 MB per file· Up to 20 files· Deleted after 30 minutes
Files are processed on our servers and deleted after 30 minutes.
STL and OBJ store no units. If a part shows up 10× or 25.4× too small or too big in the slicer, the units were read wrong — set them here.
Blender, CAD programs and slicers use Z-up; glTF, Unity and most game engines use Y-up. Switch it if the model lies on its side after import.
Used when converting STEP or IGES solids to a mesh. Fine gives smooth curves but larger files; coarse is enough for quick previews.
Only used for PNG, JPG or SVG input. Relief raises dark areas; a lithophane is a thin panel that shows the photo when lit from behind; extrude turns a logo or SVG outline into a flat solid shape.
Width of the printed model; the height follows the image's aspect ratio.
Maximum raised height for a relief or lithophane, or the thickness of an extruded shape. Lithophanes usually use 2–3 mm.
Solid plate under the relief so the print holds together. 0 means no base.
How to use this tool
- 1
Upload the OBJ
Drop the .obj file. The .mtl and texture images are not needed for STL, because STL cannot store color. Up to 20 models, 95 MB each.
- 2
Check scale and parts
Under Advanced settings, set Model units to the unit the model was built in; Blender scenes use meters. Merge into one mesh is on, which suits a single print; turn it off to keep parts apart.
- 3
Convert to STL
Press Convert to STL and open the file in your slicer. Measure one dimension before you slice.
OBJ is a modeler's format and STL is a printer's format. The conversion keeps the shape, splits every face into triangles and leaves behind the materials, UV maps and smoothing groups that a slicer would ignore anyway.
What changes when you convert OBJ to STL
Wavefront Technologies defined OBJ in the late 1980s for its Advanced Visualizer software, and the plain-text layout has outlived the company. An OBJ lists vertices, texture coordinates and normals, then faces that may have three, four or more corners. Materials live in a separate .mtl file that points to texture images, which is why OBJ downloads often arrive as a folder or a ZIP; ZIP to STL converts such an archive without unpacking it first.
STL keeps only triangles. During conversion, quads and n-gons are split, vertex normals are replaced by one normal per facet, and the groups and objects of the OBJ are written as one model, or kept apart when Merge into one mesh is off. Neither format stores units, so scale is the part to watch: the numbers are copied as they are and the slicer decides they are millimeters.
OBJ
Wavefront OBJ
OBJ is a 3D geometry format developed by Wavefront Technologies. It is a plain-text file listing vertices, texture coordinates, normals and faces, with materials and textures referenced in a separate .mtl file. Almost every 3D modelling program, game engine and 3D printing tool can import it. OBJ does not support animation, rigging or scene hierarchies, and textures go missing if the MTL and image files are not kept together.
- Compression
- –
- Transparency
- –
- Animation
- No
- Introduced
- Wavefront Technologies
STL
STL mesh
STL (stereolithography) is a 3D mesh format created by 3D Systems in 1987. It describes only the surface geometry of an object as a list of triangles, without colour, materials, units or scene information. Its simplicity makes it the default input for 3D printing slicers such as Cura and PrusaSlicer. Curved surfaces are approximated by many flat triangles, so smooth models can produce very large files.
- Compression
- –
- Transparency
- –
- Animation
- No
- Introduced
- 1987 · 3D Systems
People convert OBJ to STL when a model made for rendering, games or scanning has to go to a printer, a print service or an upload form that only lists STL.
Does Cura, PrusaSlicer or Bambu Studio need STL?
| Organisation | Requirement | Source |
|---|---|---|
| Ultimaker Cura | STL, OBJ, 3MF and X3D, plus PNG and JPG as height maps. OBJ textures are ignored. | — |
| PrusaSlicer | STL, OBJ, 3MF and AMF; STEP since version 2.6. OBJ colors can be mapped to filaments in recent versions. | — |
| Bambu Studio | STL, OBJ, 3MF and STEP. Multi-color painting is saved in its own 3MF projects. | — |
| Print services and model libraries | Most upload forms list STL first; some accept OBJ or 3MF, few accept textured OBJ folders. | — |
Fixing an OBJ that will not print after converting
The model is the size of a grain of rice
The OBJ was saved in meters, typically from Blender or a game engine. Set Model units to m and convert again.
The slicer reports non-manifold edges
The mesh has holes or single-sided surfaces. Close them with Blender's 3D Print Toolbox or the slicer's repair command before printing.
The figure is lying on its back
The model was exported Y-up. Set Up axis to Z-up so it stands on the bed.
Parts float or overlap
Separate objects were merged. Turn off Merge into one mesh and arrange them in the slicer, or join them with a boolean union in Blender.
OBJ to STL questions
Why is my Blender OBJ tiny after converting to STL?
Blender treats one unit as one meter, so a 40 mm figurine is written as 0.04. Slicers read STL numbers as millimeters and show a speck. Set Model units to m and convert again, and the part comes out at 40 mm.
What happens to the textures and colors of my OBJ?
They are left behind. STL stores geometry only, so the .mtl materials and image textures have nowhere to go. If you want the colors for a multi-color printer, use 3MF; for viewing in a browser or AR, OBJ to GLB keeps the textures.
My OBJ has quads and n-gons. Is that a problem?
No. OBJ can store faces with any number of corners, while STL accepts only triangles, so every face is split into triangles during conversion. The shape stays the same; only the triangle count rises.
Why does the slicer say the converted model has errors?
Models built for games and rendering often have open edges, overlapping pieces or single-sided planes such as leaves and hair cards. They render fine but do not describe a closed volume. Repair them in Blender with the 3D Print Toolbox add-on, or let PrusaSlicer or Bambu Studio fix them on import.
Is a sculpt with millions of polygons too big for STL?
Binary STL uses 50 bytes per triangle, so a 2-million-triangle sculpt is about 100 MB, just over the 95 MB upload limit. Decimate it in Blender or ZBrush first; most printers cannot reproduce detail that fine anyway.
- STL to OBJ ConverterConvert STL to OBJ for Unity, texturing tools and other 3D apps that expect OBJ. Shared vertices, readable text and the same triangles, in seconds.
- FBX to OBJ ConverterConvert FBX files from Mixamo, Unity asset packs or Maya to OBJ with MTL materials and textures. Binary and ASCII FBX accepted, 20 files per batch.
- 3MF to STL ConverterConvert 3MF to STL for slicers, print services and tools that only read STL. Geometry is kept in millimeters; colors, plates and print settings drop out.
- STEP to STL ConverterConvert STEP or STP files to STL for Cura, PrusaSlicer and Bambu Studio. Pick coarse, normal or fine mesh detail and get a binary STL in millimeters.
- OBJ to GLB ConverterConvert OBJ with its MTL and textures into a single GLB for three.js, model-viewer, Shopify and Android AR. Scale set to meters, materials embedded.
- Image to STL ConverterTurn a JPG, PNG, WebP or BMP image into a printable STL: a raised relief, a backlit lithophane or a flat extruded shape. Set width, depth and base in mm.
