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STL 3MF
Free online converter

Convert STL to 3MF

Convert now
STL to 3MF converterFREE
Drop a .STL file here
or pick one - we convert it to .3MF and give you the file to download

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Tested on macOS, Windows & Linux
Last verified Oct 2026

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How to convert STL to 3MF

  1. Add your .STL file - drop it in the box above or click to browse.
  2. Convert it to .3MF in a few seconds.
  3. Download your new .3MF file.

What to expect

  • 3MF stores the same triangle mesh as STL - geometry transfers without loss.
  • Units are baked in on export: if your STL was modeled in inches and the slicer assumes millimeters, rescale before saving.
  • Mesh errors carry over - non-watertight geometry or flipped normals in the STL will appear in the 3MF; use 3D Builder or PrusaSlicer's repair tool to fix them first.

Frequently asked questions

Is the conversion lossless?
The triangle mesh is identical in the output 3MF. You gain a unit declaration but cannot gain data never stored in STL, such as color or material assignments.
Why is my model the wrong size after converting?
STL carries no unit information - if the original used inches and the slicer assumed millimeters (or vice versa), the model will be 25.4x off; rescale it in the slicer before exporting.
Can I convert a `3MF` back to `STL`?
Yes - PrusaSlicer, Bambu Studio, and Cura all open 3MF and export as STL.
Do all slicers support `3MF`?
PrusaSlicer, Bambu Studio, and Ultimaker Cura support 3MF natively; older or niche slicers may still require STL.
Learn about the formats: .STL · .3MF