# OBJ to STL Converter

> To convert OBJ to STL, load the .obj, triangulate its faces and write them to an STL file. Kenerate's free converter does it in your browser: drop the OBJ, preview it, fit the longest side to a size in millimetres and turn it Z-up, then download a binary STL. Materials and UVs are dropped. Nothing is uploaded.

URL: https://kenerateai.com/obj-to-stl
Publisher: Kenerate AI (https://kenerateai.com)
Last updated: 2026-10-01

## Key facts
- Price: Free, no account
- Converts: Wavefront OBJ → binary STL
- Faces: Quads and n-gons triangulated
- Dropped: Materials (.mtl), UVs, smoothing groups
- Scale: Keep units or fit longest side to 25–200 mm
- Privacy: Converted locally — no upload
- Smaller files: OBJ is text; binary STL stores each triangle in 50 bytes. The same mesh is often several times smaller as STL.
- One clean mesh: Every object and group in the OBJ is merged into one STL in its original position.
- Size it for print: OBJ has no units. Fit the longest side to the size you want and print without rescaling in the slicer.
- Check before printing: The Clay and Wire views show holes, thin walls and messy scan areas before you waste filament.
- Parse: Vertices and faces are read from the OBJ text; quads and n-gons are split into triangles.
- Merge: Objects and groups are combined in their original positions.
- Scale and orient: Optionally fit to a size in millimetres and turn Z-up.
- Write: A binary STL is generated and downloaded.
- OBJ (Wavefront OBJ): Plain-text mesh; by Wavefront Technologies, 1980s. Holds: Vertices, faces, UVs and normals, Materials via a separate .mtl file. Lacks: Animation and rigs, Embedded textures. Best for: Moving static meshes between 3D apps. Opens in: Blender, Maya, 3ds Max, ZBrush, most slicers.
- STL (Stereolithography): Triangle mesh (binary or ASCII); by 3D Systems, 1987. Holds: Triangle surfaces, Facet normals. Lacks: Colour and textures, Units, Materials. Best for: 3D printing — every slicer opens it. Opens in: Cura, PrusaSlicer, Bambu Studio, OrcaSlicer, Blender.
- Encoding — OBJ vs STL: Text | Binary (or text)
- Faces — OBJ vs STL: Triangles, quads, n-gons | Triangles only
- UVs and materials — OBJ vs STL: Yes (UVs in file, materials in .mtl) | No
- Units — OBJ vs STL: None | None
- Typical use — OBJ vs STL: Moving meshes between 3D apps | 3D printing

## Steps
1. Open the OBJ — Drop your .obj onto the box above, or try the sample mug.
2. Preview — Orbit it and check the triangle count.
3. Set options — STL is selected. Choose a size in mm if you need one; keep Z-up for slicers.
4. Download — Click Download STL.

## In depth

### Do slicers need STL?
Not always — PrusaSlicer, Cura and others read OBJ directly. STL is still the safest choice for print services, older tools and printer-specific software, and its binary form is compact [1].

### Quads, n-gons and triangulation
OBJ can store faces with any number of corners [2]; STL only stores triangles [1]. Triangulating doesn't change the shape — it only splits flat faces — so a print looks the same.

References:
[1] Wikipedia — STL (file format): https://en.wikipedia.org/wiki/STL_(file_format)
[2] Wikipedia — Wavefront .obj file: https://en.wikipedia.org/wiki/Wavefront_.obj_file
[3] Wikipedia — FBX: https://en.wikipedia.org/wiki/FBX
[4] Khronos Group — glTF: https://www.khronos.org/gltf/
[5] 3MF Consortium — 3MF specification: https://3mf.io/specification/
[6] Wikipedia — Universal Scene Description (USD / USDZ): https://en.wikipedia.org/wiki/Universal_Scene_Description
[7] Wikipedia — PLY (file format): https://en.wikipedia.org/wiki/PLY_(file_format)
[8] Khronos Group — glTF 2.0 specification: https://registry.khronos.org/glTF/specs/2.0/glTF-2.0.html
[9] Apple — AR Quick Look: https://developer.apple.com/augmented-reality/quick-look/
[10] three.js — documentation: https://threejs.org/docs/
[11] Prusa Knowledge Base — Modeling with 3D printing in mind: https://help.prusa3d.com/article/modeling-with-3d-printing-in-mind_164135
[12] Prusa Blog — lithophanes and filament transparency: https://blog.prusa3d.com/lets-play-with-filament-transparency-how-to-make-amazing-lifelike-color-photos-with-just-a-simple-color-change_104338/
[13] Polymers (2024) 16(20):2862 — FFF parameters and translucency of PLA: https://doi.org/10.3390/polym16202862
[14] Wikipedia — Lithophane: https://en.wikipedia.org/wiki/Lithophane
[15] W3C — CSS Values and Units Level 3 (absolute lengths): https://www.w3.org/TR/css-values-3/
[16] Adobe Substance 3D — OpenGL vs DirectX normal maps: https://experienceleague.adobe.com/en/docs/substance-3d/bakers/common-questions/what-is-the-difference-between-the-opengl-and-directx-normal-format
[17] Blender Manual — Normal Map node: https://docs.blender.org/manual/en/latest/render/shader_nodes/displacement/normal_map.html
[18] Wikipedia — Normal mapping: https://en.wikipedia.org/wiki/Normal_mapping
[19] SIL Open Font License: https://openfontlicense.org/

## FAQ
Q: Is OBJ to STL conversion free?
A: Yes. It runs in your browser with no account or watermark.

Q: Is my OBJ uploaded?
A: No — it's converted on your device.

Q: Do I need the .mtl file?
A: No. STL can't store materials, so only the .obj is needed.

Q: What happens to quads?
A: They're split into two triangles each. The shape doesn't change.

Q: My STL is the wrong size — why?
A: OBJ has no units. Choose “Fit longest side to” a size in millimetres before downloading.

Q: Can I keep colours?
A: Not in STL. Convert to 3MF or GLB if colour matters.

Q: How do I convert OBJ to STL in Blender?
A: Import the OBJ with File → Import → Wavefront (.obj), select the model, then use File → Export → STL (.stl) and tick Selection Only if the scene has other objects. Check the scale first, because OBJ has no units. Or skip Blender: drop the OBJ here and set the size in millimetres.

## Related pages
- AI 3D Model Generator: https://kenerateai.com/ai-3d-model-generator
- Image to 3D: https://kenerateai.com/image-to-3d-converter
- AI STL Generator: https://kenerateai.com/ai-3d-printing-model-generator
- Text to 3D: https://kenerateai.com/text-to-3d-generator

## Sources
- Wikipedia — STL (file format): https://en.wikipedia.org/wiki/STL_(file_format)
- Wikipedia — Wavefront .obj file: https://en.wikipedia.org/wiki/Wavefront_.obj_file
- Wikipedia — FBX: https://en.wikipedia.org/wiki/FBX
- Khronos Group — glTF: https://www.khronos.org/gltf/
- 3MF Consortium — 3MF specification: https://3mf.io/specification/
- Wikipedia — Universal Scene Description (USD / USDZ): https://en.wikipedia.org/wiki/Universal_Scene_Description
- Wikipedia — PLY (file format): https://en.wikipedia.org/wiki/PLY_(file_format)
- Khronos Group — glTF 2.0 specification: https://registry.khronos.org/glTF/specs/2.0/glTF-2.0.html
- Apple — AR Quick Look: https://developer.apple.com/augmented-reality/quick-look/
- three.js — documentation: https://threejs.org/docs/
- Prusa Knowledge Base — Modeling with 3D printing in mind: https://help.prusa3d.com/article/modeling-with-3d-printing-in-mind_164135
- Prusa Blog — lithophanes and filament transparency: https://blog.prusa3d.com/lets-play-with-filament-transparency-how-to-make-amazing-lifelike-color-photos-with-just-a-simple-color-change_104338/
- Polymers (2024) 16(20):2862 — FFF parameters and translucency of PLA: https://doi.org/10.3390/polym16202862
- Wikipedia — Lithophane: https://en.wikipedia.org/wiki/Lithophane
- W3C — CSS Values and Units Level 3 (absolute lengths): https://www.w3.org/TR/css-values-3/
- Adobe Substance 3D — OpenGL vs DirectX normal maps: https://experienceleague.adobe.com/en/docs/substance-3d/bakers/common-questions/what-is-the-difference-between-the-opengl-and-directx-normal-format
- Blender Manual — Normal Map node: https://docs.blender.org/manual/en/latest/render/shader_nodes/displacement/normal_map.html
- Wikipedia — Normal mapping: https://en.wikipedia.org/wiki/Normal_mapping
- SIL Open Font License: https://openfontlicense.org/