# STL to 3MF Converter

> To convert STL to 3MF, read the STL's triangles, weld shared corners into one mesh and write it into a 3MF package with a unit. Kenerate's free converter does it in your browser: drop the .stl, optionally fit its longest side in millimetres, and download a .3mf for Bambu Studio, PrusaSlicer, OrcaSlicer or Cura. Nothing is uploaded.

URL: https://kenerateai.com/stl-to-3mf
Publisher: Kenerate AI (https://kenerateai.com)
Last updated: 2026-10-01

## Key facts
- Price: Free, no account
- Converts: Binary or ASCII STL → 3MF package (ZIP + XML), unit = millimetre
- Mesh: Shared vertices welded into one connected object
- Scale: Keep the STL's numbers as mm, or fit longest side to 25–200 mm
- Colour: None added — the STL had none
- Privacy: Converted locally — no upload
- Size you can trust: 3MF stores its unit. Once a model is millimetres in the file, every slicer opens it at the same size.
- Smaller files: 3MF is a compressed ZIP and shares vertices between triangles, so it's usually much smaller than the STL.
- Connected mesh: STL repeats every corner for every triangle. Welding them gives slicers a mesh they can check for holes.
- Ready for colour later: Paint the 3MF in Bambu Studio or PrusaSlicer for multi-colour printing — STL can't hold that.
- Parse: Triangles are read from the binary or ASCII STL.
- Scale: Optionally fit the longest side to your chosen size in millimetres.
- Weld: Identical corners are merged so the triangles share vertices.
- Package: The mesh is written as 3MF XML with unit="millimeter" and zipped.
- 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.
- 3MF (3D Manufacturing Format): ZIP package with XML; by 3MF Consortium, 2015. Holds: Meshes with units (millimetres), Colours and materials, Several objects and build plates. Lacks: Animation. Best for: Modern 3D printing and multi-colour prints. Opens in: Bambu Studio, PrusaSlicer, OrcaSlicer, Cura, Windows 3D Builder.
- Units — STL vs 3MF: None | Stored (millimetres here)
- Vertices — STL vs 3MF: Repeated per triangle | Shared between triangles
- Compression — STL vs 3MF: None | ZIP
- Colour and materials — STL vs 3MF: No | Yes
- Several objects and settings — STL vs 3MF: No | Yes
- Support — STL vs 3MF: Universal | All major modern slicers

## Steps
1. Open the STL — Drop your .stl onto the box above, or try the sample dragon.
2. Check it — Orbit the model and read its size.
3. Choose 3MF and a size — 3MF is selected. Keep units, or fit the longest side in mm.
4. Download — Click Download 3MF and open it in your slicer.

## In depth

### 3MF in short
The 3MF Consortium published 3MF in 2015 as a full replacement for STL in additive manufacturing [5]. It's a ZIP package whose main part is an XML model listing shared vertices and triangles indexing into them, with a declared unit [5].

### Why units matter
An STL saying “50” could mean 50 mm or 50 inches [1]; 3MF says which [5]. That ends the classic problem of a model importing 25.4× too small or too large.

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 STL to 3MF conversion free?
A: Yes — free, no account, nothing uploaded.

Q: Which slicers open the 3MF?
A: Bambu Studio, PrusaSlicer, OrcaSlicer, Cura and Windows 3D Builder all open standard 3MF files.

Q: What size will the model be?
A: The STL's numbers are treated as millimetres unless you choose a size. Pick “Fit longest side to” to set it exactly.

Q: Will it add colours?
A: No. The STL had no colour. Paint the model in your slicer after opening the 3MF.

Q: Will it fix a broken STL?
A: Welding joins identical corners, which helps slicers analyse the mesh, but it doesn't fill holes. Use your slicer's repair if needed.

Q: Is my STL uploaded?
A: No. It's converted on your device.

Q: Is 3MF better than STL?
A: For printing, usually yes: 3MF stores its unit, shares vertices in a compressed package and can hold colours, several objects and slicer settings. STL's strength is that practically every 3D tool opens it. Keep 3MF for your own slicer and share STL when a tool needs it.

## 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/