Convert 3MF to STL
Convert 3MF to STL in your browser. The STL keeps the shape in millimetres and drops colour, part names and print settings. Nothing is uploaded.
Result
Before you convert: what this keeps and what it destroys
Preserved
- The geometry, triangle for triangle
- Overall dimensions and proportions
- Watertightness, where the input is watertight
Destroyed
- A recorded unit: STL stores none
- Colour
- The separation between parts, merged into one body
- Texture images and texture coordinates, if present
↺ the reverse: STL → 3MF · about .3mf · about .stl · just view it instead
Do you need STL, or can your slicer open the 3MF?
If you are printing at home you probably do not need to convert. PrusaSlicer, OrcaSlicer and Bambu Studio open 3MF directly, and Cura reads it too. Convert when the other end accepts only STL: an older print service's upload form, a legacy slicer, or a tool that predates 3MF.
What the STL keeps
The shape: the same triangles, placed where the 3MF's build put them, in one file. The STL is written in millimetres. If the 3MF declared inches, centimetres, metres or microns, every coordinate is rescaled so the model still measures the same in a slicer that reads STL as millimetres. A 3MF with no unit is read as millimetres, which is the 3MF specification's default.
Every object that the 3MF places in the build ends up in the one STL, including models that a slicer stores in separate parts of the package. An object that is defined in the file but not placed in the build is left out.
What you lose
- Colours and materials. STL has nowhere to keep them.
- Part names and grouping. Several objects become one body, although separate pieces stay separate surfaces.
- The unit declaration. STL has none, so the receiving slicer has to read the numbers as millimetres.
- Print settings, plate layout, supports and printer profiles, which a slicer keeps in 3MF extensions.
What to check afterwards
Open the STL in the STL viewer and compare the size with the size you saw in the source. Check the triangle count and whether the mesh is reported as watertight. In your slicer, confirm the size and orientation before slicing. If the STL is empty, has fewer parts than you expect, or the parts are not where they should be, export the STL from the program that made the 3MF instead.
Questions people ask
Can I convert a 3MF file to STL online? Yes. This page does it in your browser. Nothing is uploaded and there is no account.
Is 3MF the same as STL? No. Both hold triangles, but 3MF also records a unit, colours and separate parts, and a slicer project adds print settings.
Can you 3D print a 3MF file? Yes. 3MF is the native project format of PrusaSlicer, OrcaSlicer and Bambu Studio, and Cura reads it too. Convert only if something downstream takes STL alone.
The conversion runs in your browser. Your file stays on your computer and is not uploaded.
Going the other way
Convert STL back to 3MF. The reverse conversion also works with mesh geometry. It does not reconstruct exact CAD surfaces. Material data and part structure lost in either direction cannot be restored by converting back. Keep the original file for later edits.
How we know this conversion works
This pair was checked against 13 files from the test corpus on 2026-09-07. Each run parses its own output back in and compares the bounding box, the triangle count and, for closed solids, the volume against the input.
A pair that fails those checks doesn't get a page. That's why this site lists 120 conversions and not the several hundred a format-times-format grid would suggest.