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3DAI
Free · runs in your browser · no signup

Convert OBJ to STL for 3D Printing

OBJ is the long-standing exchange format from modelling tools like Blender, Maya, ZBrush and many scanners. To print an OBJ you need it as STL. This tool reads the .obj file on your own device, triangulates it and gives you an STL ready for the slicer.

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How to use it

  1. 1

    Add your .obj

    Drag it onto the box or click to choose it. You only need the .obj; the .mtl and texture files are not used.

  2. 2

    Look it over

    Rotate the preview and check the size and watertight readout before you download.

  3. 3

    Pick the options

    Choose binary or ASCII, a scale if your OBJ was modelled in cm, inches or metres, and whether to stand it upright.

  4. 4

    Download and slice

    Save the STL and open it in Cura, PrusaSlicer, Bambu Studio or any other slicer.

What to know before you convert

  • Only geometry is kept. The .mtl file, textures, UVs and normals are not part of STL and are ignored.
  • Quads and larger polygons are split into triangles. The shape does not change.
  • All objects and groups are merged into one STL file, each as its own shell.
  • Free-form curves and surfaces (curv, surf) and line elements are not supported, only polygon faces.
  • Holes and bad faces are not repaired. Check the watertight line in the info panel.

Don't have a model?

Generate one from a sketch, image or text. Our AI generators give you a 3D model with an STL download for printing. They use credits; this converter does not.

Sketch to STL →Draw it, get a printable model.Image to STL →One photo of an object.Text to STL →Describe it in a sentence.

Frequently Asked Questions

No. STL cannot store materials or textures, so only the .obj file is read. The colours you see in other viewers come from the .mtl and will not appear in the STL.
No. STL only allows triangles, so each quad becomes two triangles and larger polygons are fanned into triangles. The surface stays the same; the triangle count in the panel goes up.
Neither OBJ nor STL stores units. The numbers are copied as they are and slicers read them as millimetres. If you modelled in centimetres, inches or metres, choose the matching scale so the print comes out the right size.
The preview uses flat shading, like a slicer, so you see the real triangles. STL has no smooth normals; the actual print depends on the triangle density, not on shading.
Not on this page. It converts one file at a time. Load the next file with "Choose another file" after you download.
No. The page reads the file and converts it inside your browser with the open-source three.js library. Nothing is sent to our servers, there is no account, and no credits are used. Closing the tab discards everything.