3MF to STL converter

Drop the .3mf file onto the converter at the top of this page, check the object count, the size in millimetres and the preview, then press Download STL. The page unzips the 3MF in your browser, applies the position of every object and the unit written in the file, merges the meshes and writes a binary STL in millimetres. There is no sign-up and no queue.

Drop the .obj file onto the same converter. An OBJ file has no unit, so pick what one unit in your file means: millimetres, centimetres, metres or inches. The bounding box and the preview update at once, so you can see whether the size is right before you download. Quads and larger polygons are split into triangles. PLY and GLB files work the same way.

STL is the oldest and most widely accepted mesh format. Some CAD and mesh tools, older slicers and print services accept only STL or read 3MF incompletely. A 3MF saved from a slicer also carries a plate layout and settings you may not want to pass on, while the STL holds the geometry only. If your tool reads 3MF, keep it: 3MF is the richer format, with units, colours and separate objects.

No. STL stores triangles only. Colours, materials and textures from a 3MF, OBJ, PLY or GLB are dropped, and the geometry is kept. If you print in several colours, keep the 3MF for the slicer and use the STL where the shape is enough.

A 3MF declares its unit in the file (micron, millimeter, centimeter, inch, foot or meter, and millimeter when it says nothing), and this converter scales it to millimetres. In the test, a box saved as 1 x 0.5 x 0.25 inch came out as 25.400 x 12.700 x 6.350 mm. OBJ and PLY carry no unit at all, so you choose it on the page, with millimetres as the default, which is what most slicers assume when they open an STL. The glTF specification defines its unit as one metre, so a GLB from an exporter that follows it needs m. The bounding box tells you at once if the size is off by a factor of 1000.

Yes. There is no account, no daily limit and no watermark on the output.

No. The file is read inside your browser tab and converted by code that runs on your own machine. The page sends no file and no model data anywhere, which matters when the geometry belongs to a client or is under NDA.

STL has no separate objects, so the objects are merged into one mesh. They keep their positions, for example the plate layout of a slicer project. If you need every object as its own file, tick One STL per object and you get a ZIP with one STL for each.

The glTF format uses Y as the up axis, while slicers use Z. The converter does not rotate the model, so a standing model can appear lying down. Rotate it in your slicer, or check the preview on this page, which shows the mesh as it will be saved.

Yes, with the STL to STEP converter. Convert here first, then open the STL there. The STEP file it makes from triangles is free and is created in your browser. If you want an editable CAD model with planes, cylinders and holes recognised, Editable CAD on that page costs 4.90 EUR per file, after a free preview.