STL to 3MF Converter

Wrap STL files in 3MF, the format Bambu Studio, OrcaSlicer and PrusaSlicer save in: explicit millimetres, a welded mesh, and usually less than half the file size.

  • Files stay on your device
  • Free, no sign-up
  • Units and up axis handled
  • Batch and .zip

Drop an STL file to convert

One file, many, or a .zip

In: STL · STEP · IGES · OBJ · 3MF · GLB · glTF · PLY · FBX · DAE · 3DS · AMF · VRML · ZIP

Converted on your device. Nothing is uploaded.

    How to convert STL to 3MF

    1. Drop your STL files

      Drop one or more .stl files, binary or ASCII, or a .zip of them.

    2. Check the preview

      The model appears at the size and orientation it will have. Fix the file units, up axis or size under Size, units and orientation if needed.

    3. Choose 3MF options

      Keep parts as one object for a simple print, or tick separate objects to move them independently in the slicer.

    4. Convert and download

      One file downloads straight away. A batch gives a download per file and one .zip of all of them.

    What carries over from STL to 3MF

    Worked out from what each format can store and what this converter writes. Nothing is changed silently: the preview shows the size and orientation before you download.

    Geometry Every triangle is kept at full precision.
    Color STL has no color to carry. The 3MF comes out uncolored.
    Units Both are in millimetres, so sizes are unchanged.
    Orientation Both are Z up, so it stays the right way up.
    Objects One object by default, or one 3MF object per part. Placed on Z = 0 and centered on a 256 mm plate.

    STL to 3MF: what actually happens

    3MF holds the same triangles as STL, but in a zipped XML model that states its unit outright, so the part opens at the right size in any slicer. Because the mesh is compressed and its vertices shared, a 3MF is typically a quarter to half the size of the binary STL it came from (26% for our 60,000-triangle test model).

    The converter welds the STL's loose triangles into a connected mesh, rests the part on Z = 0 and centers it on a 256 mm plate. If the STL was modelled in inches, set the file units to inches first: the 3MF then stores true millimetres and nobody has to guess again.

    STL at a glance

    Stereolithography (Standard Triangle Language) · .stl

    Stores
    Loose triangles: three corners and a normal each, binary or ASCII
    Color
    None in the standard
    Units
    None written; slicers assume millimetres
    Up axis
    Z, the slicer convention
    File size
    50 bytes per triangle in binary, about 5 times that as ASCII
    Opens in
    Every slicer, CAD tool and 3D app

    Created by 3D Systems in 1987 for the first stereolithography printers, STL is still the format every slicer and print service accepts. It describes a surface as a list of independent triangles, with no shared vertices, units, colors or scene structure.

    Open STL files in the viewer

    3MF at a glance

    3D Manufacturing Format · .3mf

    Stores
    A zipped XML model: shared vertices, objects with transforms, a build plate
    Color
    Materials and per-triangle colors; slicers add painted filament colors
    Units
    Declared in the file, millimetres by default
    Up axis
    Z
    File size
    Compressed, usually under half of a binary STL
    Opens in
    Bambu Studio, OrcaSlicer, PrusaSlicer, Cura, Creality Print

    The 3MF Consortium (founded 2015 by Microsoft, Autodesk, HP and others) designed 3MF to replace STL for printing. Bambu Studio, OrcaSlicer and PrusaSlicer save whole projects in it: plates, painted colors and print settings alongside the meshes.

    Open 3MF files in the viewer

    Tips for STL to 3MF

    Smaller uploads

    A 24 MB STL typically comes out 6 to 12 MB as 3MF, which helps with print farms, email and cloud uploads.

    Units travel with it

    Unlike STL, 3MF says it is in millimetres. Fix inch or metre models once, here, and the size sticks.

    Add colors after

    STL has no color. Paint filament colors in your slicer or in the 3D model painter.

    STL to 3MF FAQ

    Is 3MF better than STL for 3D printing?
    For most jobs, yes: explicit units, smaller files, several objects in one file and room for colors and print settings. STL is still the most widely accepted, so keep it when a print service asks for STL.

    Will the 3MF include print settings?
    No. It is a clean model file. Choose your printer, filament and process in the slicer as usual.

    Can I convert many STLs to 3MF at once?
    Yes. Drop them all, or a .zip, and download every 3MF in one .zip.

    Is the converter free? Are there limits?
    Free, with no sign-up, watermark or file count limit. Batches and files of a few hundred MB work on most laptops; the only limit is your device's memory.

    Are my files uploaded?
    No. Files are read and written by JavaScript and WebAssembly in your browser and never sent to PrintPal. The STEP and IGES reader is the only extra download, once, from a public CDN.