STL to 3MF converter
Drop your .stl file — we convert it to .3mf right in your browser. Files never leave your computer.
Why convert STL to 3MF?
STL strips everything except triangles. 3MF adds back units, colour, and multi-body metadata. Moving a library from STL to 3MF cleans up the ongoing unit-ambiguity headache and unlocks features every modern slicer (Bambu Studio especially) relies on.
Who runs this conversion
Makers migrating their print libraries to Bambu Studio / OrcaSlicer defaults, print services that want metadata-rich uploads, and anyone tired of guessing whether a downloaded STL was saved in millimetres or inches.
Things that commonly go wrong
- 3MF assumes millimetres. An imperial STL will land at 25.4× intended size unless you rescale first — check dimensions before slicing.
- Slicer-specific print settings do not get embedded; this tool writes plain 3MF (no Bambu/PrusaSlicer bed layout).
- Multi-body 3MF is possible, but an STL carries only one triangle soup — the output is a single body.
Technical note for this tool
STLLoader → welded BufferGeometry → minimal 3MF package per the Consortium core spec (zip + 3dmodel.model XML + .rels). Units tagged millimetres.
STL vs 3MF— what's the difference?
Triangle-mesh format that every 3D printer slicer understands. Geometry only — no units, colours, or assemblies.
- Universal 3D printing format — Cura, PrusaSlicer, Bambu Studio all speak STL
- Tiny, simple, extremely fast to load
- Great for meshing workflows, simulation pre-processors, quick previews
- Triangulated approximation — curved surfaces lose precision
- No colour, material, or assembly data
- One shell per file by convention (multi-body gets flattened)
Modern successor to STL for 3D printing — carries units, colours, materials, and multiple bodies in a zipped XML package.
- Real-world units baked in (no more "is this mm or inches?")
- Multi-material, multi-colour, and per-body metadata
- Compact zipped payload — smaller than equivalent STL
- Not every slicer reads 3MF yet (most do now — Bambu, Prusa, Cura)
- Less tooling for mesh editing compared to STL
Deeper context on the formats
STL — where it came from
Invented by 3D Systems in 1987 for the first commercial stereolithography machine (hence the name — "STereoLithography"). It was supposed to be a throwaway internal format; nearly four decades later it is still the default hand-off between CAD and every slicer on the market, simply because nothing else got universal support in time.
- STL has no units — a file authored in inches and re-opened in a metric slicer prints at 1/25.4 scale. Always confirm the source units before slicing.
- Non-manifold meshes (holes, flipped normals, internal walls) slice silently but print as unsolvable garbage. Run the mesh-repair tool before wasting filament.
- ASCII STL is ~5× larger than binary STL with zero benefit — always export binary unless you specifically need to diff the file.
Real-world use: Every FDM and SLA slicer (Cura, PrusaSlicer, Bambu Studio, Lychee, Chitubox) reads STL as a first-class input. Simulation pre-processors (Ansys, Abaqus) also consume STL for meshing. Fabrication-on-demand services (Shapeways, JLCPCB's 3D print arm, Protolabs) accept STL uploads directly.
3MF — where it came from
The 3MF Consortium (Microsoft, HP, Autodesk, Dassault, Shapeways, and others) published version 1.0 in 2015 specifically to replace STL's forty-year-old limitations. Bambu Studio and PrusaSlicer adopted it aggressively because it is the only portable way to ship multi-colour / multi-material print projects.
- The format is zipped XML — renaming .3mf to .zip and inspecting the contents is fair game for debugging.
- Extensions (materials, slice, production) are optional; a slicer may read the geometry but drop the colour metadata.
- Some slicers treat "print-ready 3MF" (baked supports and toolpaths) differently from "design 3MF" (just the mesh). Check the export dialog for the right flavour.
Real-world use: Multi-material Bambu X1C / A1 prints, Prusa MMU workflows, paint-by-face colour printing (PrusaSlicer, Bambu Studio), and Windows 3D Builder. Anywhere an STL would lose information, 3MF has quietly taken over.
How to convert STL to 3MF
- 1Drop a .stl file onto the page. Binary or ASCII STL both parse. Nothing leaves your browser.
- 2Confirm the mesh looks right in the preview — orient, zoom, inspect the triangle count.
- 3Click Download .3MF. Load it directly in Bambu Studio, PrusaSlicer, Cura, or OrcaSlicer.
FAQ
Why convert STL to 3MF?
3MF is the modern replacement for STL in 3D printing. It carries real-world units, colour, multi-material bodies, and metadata — STL carries none of that. Every current slicer (Bambu Studio, PrusaSlicer, Cura, OrcaSlicer) prefers 3MF when it is available.
Will my STL lose precision converting to 3MF?
No — 3MF stores the same triangle mesh STL does, so the geometry is bit-identical. The gain is on the metadata side: units, model info, and multi-body packaging.
Can I set units during conversion?
STL has no units, so the converter assumes the numbers are millimetres (the 3D-printing default). If your STL was authored in inches, scale it in your slicer after importing the 3MF.
Will the 3MF be smaller than the STL?
Usually yes — 3MF zips its XML payload, so a typical binary STL shrinks 30–60% when re-packaged as 3MF.
Is anything uploaded?
No. The STL is parsed in your browser and re-packaged as 3MF locally. The file never touches a server.