Skip to content
Kenerate IconKenerate Icon
Kenerate AI
Start

Millimetres · free · nothing uploaded

Convert STL to 3MF with real units

Give an old STL the modern print format: a compact 3MF package that records its size in millimetres, so it lands on the plate at the size you meant.

  • Unit stored as millimetres
  • Set the longest side in mm
  • Welded, connected mesh
  • Free and private

Updated by the

Quick answer

Updated

How do you convert STL to 3MF?

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.

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

Why this tool

Why move an STL to 3MF

3MF was designed by the printing industry to replace STL's guesswork.

  • A 3D printer nozzle printing a grey dragon miniature layer by layer

    Size you can trust

    3MF stores its unit. Once a model is millimetres in the file, every slicer opens it at the same size.

    Try it
  • A 3D printer printing a dragon beside its wireframe

    Smaller files

    3MF is a compressed ZIP and shares vertices between triangles, so it's usually much smaller than the STL.

    Try it

Also

What else it does

  • 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.

How it works

How the STL becomes a 3MF

Built in your tab with no server.

  • 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.

How to

How to use the STL to 3MF Converter

Time needed
Steps
4 steps

  1. Step 1

    Open the STL

    Drop your .stl onto the box above, or try the sample dragon.

  2. Step 2

    Check it

    Orbit the model and read its size.

  3. Step 3

    Choose 3MF and a size

    3MF is selected. Keep units, or fit the longest side in mm.

  4. Step 4

    Download

    Click Download 3MF and open it in your slicer.

Watch the tour · 1:48

Text, photo or multi-view to a textured GLB, nine engines, the viewer & lighting, compare engines, gallery, download & chat

Chapters

Who uses it

Who converts STL to 3MF

  • Bambu and Prusa owners

    Work in your slicer's native format.

  • Model designers

    Publish files that open at the right size everywhere.

  • Print farms

    Smaller files and fixed units across machines.

  • Multi-colour printing

    Start from 3MF, then paint colours in the slicer.

Compare

STL vs 3MF

Why most modern slicers now save 3MF by default.

STL vs 3MF — checked 2026-10-01
STL3MF
UnitsNoneStored (millimetres here)
VerticesRepeated per triangleShared between triangles
CompressionNoneZIP
Colour and materialsNoYes
Several objects and settingsNoYes
SupportUniversalAll major modern slicers

File formats

The formats this tool reads and writes

What each file can hold, what it can't, and where it opens. Facts link to the format's own spec or reference page.

The formats this tool reads and writes — checked 2026-10-01
.stl · STL.3mf · 3MF
Full nameStereolithography3D Manufacturing Format
Made by3D Systems, 19873MF Consortium, 2015
KindTriangle mesh (binary or ASCII)ZIP package with XML
HoldsTriangle surfaces, Facet normalsMeshes with units (millimetres), Colours and materials, Several objects and build plates
NoColour and textures, Units, MaterialsAnimation
Best for3D printing — every slicer opens itModern 3D printing and multi-colour prints
Opens inCura, PrusaSlicer, Bambu Studio, OrcaSlicer, BlenderBambu Studio, PrusaSlicer, OrcaSlicer, Cura, Windows 3D Builder

Sources: Wikipedia — STL (file format) · 3MF Consortium — 3MF specification

No file yet?

Make the model first — from one photo

Every sample in the tool above began as a single picture and was turned into a 3D model in the Kenerate 3D Studio. The engine is named on each one.

Example uses

How creators use the STL to 3MF converter

Illustrative examples of typical workflows, not customer reviews.

  • Enclosed 3D printer printing a white planter

    Printer owner

    A printer owner can convert an old STL to 3MF so it opens in their slicer's native format at the right size.

  • Teal 3D printed desk organiser beside a steel ruler

    Model designer

    A designer can publish files as 3MF in millimetres so the model lands on the plate at the size they meant.

  • Row of 3D printers on shelving printing the same part

    Print farm

    A print farm can use smaller 3MF files with fixed units across all its machines.

FAQ

STL to 3MF Converter questions

Is STL to 3MF conversion free?

Yes — free, no account, nothing uploaded.

Link to this answer

Which slicers open the 3MF?

Bambu Studio, PrusaSlicer, OrcaSlicer, Cura and Windows 3D Builder all open standard 3MF files.

Link to this answer

What size will the model be?

The STL's numbers are treated as millimetres unless you choose a size. Pick “Fit longest side to” to set it exactly.

Link to this answer

Will it add colours?

No. The STL had no colour. Paint the model in your slicer after opening the 3MF.

Link to this answer

Will it fix a broken STL?

Welding joins identical corners, which helps slicers analyse the mesh, but it doesn't fill holes. Use your slicer's repair if needed.

Link to this answer

Is my STL uploaded?

No. It's converted on your device.

Link to this answer

Is 3MF better than STL?

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.

Link to this answer

In depth

STL to 3MF Converter, explained

What the formats really store, what changes when you convert, and how to avoid the usual print and import problems.

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].

Keep going

Other 3D viewers and converters

By Last updated and reviewed

We build the Kenerate 3D Studio and these free tools. They run on three.js in your browser, so files stay on your device; every sample model is a real output of the AI engine named on it. Technical facts link to their specs and manuals.

Sources: Wikipedia — STL (file format) · Wikipedia — Wavefront .obj file · Wikipedia — FBX · Khronos Group — glTF · 3MF Consortium — 3MF specification · Wikipedia — Universal Scene Description (USD / USDZ) · Wikipedia — PLY (file format) · Khronos Group — glTF 2.0 specification · Apple — AR Quick Look · three.js — documentation · Prusa Knowledge Base — Modeling with 3D printing in mind · Prusa Blog — lithophanes and filament transparency · Polymers (2024) 16(20):2862 — FFF parameters and translucency of PLA · Wikipedia — Lithophane · W3C — CSS Values and Units Level 3 (absolute lengths) · Adobe Substance 3D — OpenGL vs DirectX normal maps · Blender Manual — Normal Map node · Wikipedia — Normal mapping · SIL Open Font License

Try the STL to 3MF Converter

Free and private — your files never leave your device. Want to make models with AI? That's the 3D Studio, on any paid plan or credit pack.

Convert an STLAll 3D tools

Tried it? Tell us how it went