Convert 3MF to STL
Free online 3MF-to-STL converter. No sign-up, no upload, no watermark — it runs entirely in your browser.
Drop your 3MF file here
or click to browse · we convert it to STL instantly
100% in your browser — your file never leaves your device.
Nine times out of ten the 3MF I'm converting is a slicer project — a MakerWorld or Printables download that Bambu Studio or PrusaSlicer saved with plates, painted supports and every print setting baked in. What I want is the bare mesh: to open it in a different slicer, remix it in Blender or Tinkercad, or hand a print service a file it won't argue with. This strips the 3MF back to its geometry and writes one binary STL. If you're already sitting in the slicer, its own STL export is one menu away and you don't need me — this page is for the phone, the Chromebook, and the machine that doesn't have the slicer installed.
Converting 3MF (3D Manufacturing Format) to STL (stereolithography)
3MF is a modern 3D-printing format that can carry color, multiple objects and print settings in one tidy file. STL is the lowest-common-denominator format every slicer accepts. Converting 3MF to STL maximizes compatibility with older or simpler tools.
What's kept and what's dropped
The mesh geometry of your model is preserved. 3MF extras — color, multiple build items and metadata — are flattened away, since STL stores geometry only.
What this conversion is actually for
MakerWorld model, different printer
The download is a Bambu Studio project 3MF; the printer in the garage runs on Cura. Cura opens a plain 3MF fine, but a project file brings every plate's objects in at once and none of the settings mean anything to it. As STL it's just the part, and I set supports and layer height fresh for the machine that's actually printing it.
Remixing in Tinkercad or Blender
Tinkercad wants STL or OBJ before I can chop a hole in a model or add a name plate. Blender opens 3MF only with an add-on; STL it reads natively. Convert, edit, then let the slicer save the result back as a 3MF with your settings inside.
A project with three plates on it
A project file can hold several plates of parts. Everything in it gets written into one STL solid here, so if I only want one part I either delete the rest in the slicer and export that plate, or convert the whole thing and split by parts afterwards — PrusaSlicer and Bambu Studio both have Split → To objects.
Print services that want plain files
Most services take 3MF now, but the odd upload form still rejects a 3MF with painted seams, modifiers and a printer profile inside it. A plain STL has never been rejected by anything.
How to convert 3MF to STL
- 1Drop your 3MF file onto the box above, or click to browse for it.
- 2Sculptor converts it to STL right in your browser — nothing is uploaded.
- 3Your STL file downloads automatically. That's it.
Before you trust the STL: 4 checks
- Scale
- 3MF declares its unit — millimetres by default — and the numbers in the STL are the same numbers. Open the result in the STL viewer: if the readout matches the size the slicer showed, nothing moved. This is the one conversion on this site where scale is rarely the problem.
- Colour and multi-material paint are gone
- AMS or MMU colour painting lives in the 3MF, not the mesh. STL is single-colour by definition. If it's a multi-colour print, keep the original 3MF for the coloured plate and use the STL only for the tools that need it.
- Supports and settings are gone
- Painted supports, seam paint, modifiers, layer height, infill — all project data, none of it in an STL. Expect to set them again in whichever slicer you open the STL in.
- Several objects became one solid
- Multiple build items merge into a single STL solid at their placed positions. Overlapping parts are fine for printing (slicers union them); parts that were meant to print separately need splitting in the slicer.
New to these formats? Read what a 3MF file is and what an STL file is. Check the result in the free STL viewer before it goes anywhere.
3MF to STL — FAQ
- Does this work on slicer project files, or only plain 3MF?
- Both are 3MF underneath. The converter reads the model geometry — the build items and their placement, including the split-out object files a Bambu Studio project uses — and skips the project extras (settings, paint, plates). If a heavily customised project file refuses to load, export a plain copy from the slicer first: Bambu Studio → File → Export → Export Generic 3MF. PrusaSlicer → File → Export → Export Plate as STL gets you there directly.
- Will the colours survive?
- No. 3MF can carry per-triangle colours and multi-material painting; STL has no colour field at all. Every triangle comes out as bare geometry. For a coloured print keep the 3MF; for a coloured model outside the printer world, convert to OBJ instead and re-apply materials there.
- Why is the STL bigger than the 3MF was?
- A 3MF is a zip archive with the mesh stored as compressed XML; a binary STL stores 50 uncompressed bytes per triangle. Nothing has been added — the same mesh just isn't zipped any more. Zipping the STL yourself gets most of the difference back if you're emailing it.
- Will the size be right in my slicer?
- Almost always, yes. 3MF stores millimetres (or declares whichever unit was used) and slicers read STL as millimetres, so a 120 mm part stays 120 mm. Check the readout in the STL viewer once; if it's off by 25.4× the original 3MF was declared in inches, and a quick scale in the slicer fixes it.
- Can I convert STL back to 3MF here?
- Not on this site — but every slicer does it: import the STL and Save Project As, and you have a 3MF with your settings inside. That's also the right way to make a 3MF, since the value of the format is the print data the slicer adds.
- The 3MF had four objects in it — where did they go?
- Into one STL, at their original positions. STL has no notion of separate objects. If you need them apart, import the STL and use Split → To objects in PrusaSlicer or Bambu Studio, or convert each object from its own 3MF.
- Is my file uploaded anywhere while it converts?
- No. The 3MF is unzipped and parsed inside your browser tab and the STL is written there too — the only network traffic is the page's own code. A client's part under NDA never leaves the laptop.
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