Convert STL to 3MF
Convert STL to 3MF in your browser. The conversion runs on this page and the file never leaves your computer.
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
- The unit, recorded in the file
Destroyed
- Nothing either format can represent
↺ the reverse: 3MF → STL · about .stl · about .3mf · just view it instead
Why people convert STL to 3MF
This is a straight upgrade. Do it before you print.
3MF stores everything STL does plus what STL can't: the unit, so nobody has to guess millimetres, plus colour, plus separate parts with their positions. Files are usually five to ten times smaller because each vertex is stored once instead of once per triangle.
One catch: an STL has no unit, so converting to 3MF means committing to one. This site writes millimetres, which is what almost everything assumes an STL to be. If the original came out of a CAD package set to inches, the 3MF will faithfully record the wrong unit. Check the overall dimensions before you print.
What you get
You get a binary 3MF file containing the same triangles the STL file described. No geometry is added, removed or approximated: mesh-to-mesh conversion is a change of container, and this site's tests check that the triangle count comes out identical.
Carried across: the unit, recorded in the file.
The whole conversion runs on this page, in your browser. Nothing is uploaded, so there is no server that could keep a copy of your file even in principle.
What to check afterwards
- STL carries no unit. The numbers in the file are just numbers, so the conversion assumes millimetres. Check the overall dimensions of the result before you commit to machining or printing it. A file exported from a package set to inches will be 25.4 times out.
If you need something this conversion cannot give you
This pair loses very little. 3MF carries what STL carries, so the main reason to choose a different target is what the receiving software accepts.
Going the other way
Convert 3MF back to STL is the reverse page, and the round trip is close to symmetric: both are mesh formats, so the geometry survives in both directions. What does not survive twice is anything either format cannot store: a colour dropped on the way out does not reappear on the way back.
How we know this conversion works
This pair was checked against 9 files from the test corpus on 2026-09-04. 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.