AnyFormat

00 3MF → STL

3MF to STL

Reads the units the 3MF declares and scales accordingly.

Drop files or a folder here

or choose from your device · paste with ⌘V / Ctrl+V

.3mf

03Options 3

glTF works in metres and the printing formats in millimetres. Leave this on unless your model comes out a thousand times the wrong size.

Multiplied on top of any unit conversion. Use 25.4 to turn inches into millimetres.

  • No upload The conversion runs in this tab. Your file never travels — not to us, and not to the advertising.
  • No sign-up, no email, no daily cap There is no account system to sign up to.
  • No size limit we invented Only your device's memory — about ~2 GB on a desktop browser, ~400 MB on a phone.
  • Turn your Wi-Fi off and convert anyway The conversion needs nothing but this page. Ads will not load without a connection; your file will still convert. That is the whole claim, and it takes five seconds to check.

Converts 3MF to STL — usually because something downstream predates 3MF. Worth knowing before you do: 3MF is strictly the better format, and this conversion throws information away.

What you give up

3MF was designed specifically to fix what STL gets wrong, so converting the other way undoes each of those fixes.

Units. 3MF declares them; STL cannot. The declared unit is read and everything is converted to millimetres, which is what slicers assume — but the resulting file no longer says so.

Multiple objects. A 3MF can hold a whole build plate of separate parts. STL merges them into one triangle list.

Colour and materials. Per-object and per-triangle colour is part of 3MF. STL has none.

Names and metadata. Object names, the application that made it, print settings — all gone.

You may not need to convert at all

Cura, PrusaSlicer, Bambu Studio, Simplify3D, Windows 3D Builder and Microsoft 3D Viewer all read 3MF directly, most of them for years. Before converting, check whether the tool you are targeting actually needs STL — the usual reasons it genuinely does are an old firmware-side slicer, an online printing service that only accepts STL, or a piece of CAD software that never added support.

What STL cannot hold

STL is a list of triangles and nothing else. No colour, no texture, no material, no units, no object names, no scene structure — a fifty-part assembly and a single blob are the same thing to it.

It also stores every vertex once per triangle it belongs to. A cube has eight corners and is stored as thirty-six vertices, because each of the twelve triangles carries its own copy. That is why STL files are large relative to what they contain, and why the merge option exists.

If any of that matters — colour, units, separate parts — 3MF keeps all of it and is read by every current slicer.

Other names for this

Also searched as “convert 3mf to stl”, “3mf to stl for cura”.

Questions

Does my slicer really need STL?
Probably not. Cura, PrusaSlicer, Bambu Studio and Windows 3D Builder all open 3MF directly. Check before converting.
My model came out the wrong size.
The 3MF’s declared units are read and converted to millimetres. If it is still wrong, the file declares a unit that does not match how it was authored.
I had several parts and now there is one.
STL cannot keep objects separate. Convert each part to its own STL from the slicer, or keep the 3MF.
Is my model uploaded?
No. The parsing and rewriting happen in this tab. Models are frequently confidential — an unreleased product, a client’s part, a scan of something proprietary — and none of it is transmitted. Turn your Wi-Fi off and the tool keeps working.
How large a model can I convert?
There is no imposed limit; the ceiling is your device’s memory. A desktop browser handles files of roughly 2 GB and a phone about 400 MB. A 200 MB STL — around four million triangles — converts in a few seconds on a laptop.
Can I convert several models at once?
Yes — drop as many as you like, or a whole folder. Each keeps its original name with the new extension, and you can download them individually or as a ZIP.