This STL to OBJ converter saves an STL model as an OBJ file for a 3D editing app. Choose your .stl file, check the preview, and save the result. Both text-based and binary STL files work, and your file stays on your device.

Move an STL into a 3D editing app

You may have downloaded a model for printing but now want to change its shape, combine it with another model, or add colors in a 3D editor. An OBJ copy is useful when the app or workflow you use asks for that format.

If your editor already opens STL, you can also work with the original file directly. Converting is a way to change the file type, not a required step before every edit.

What changes when you convert?

STL describes a surface using small triangles. This converter can keep all of them or reduce their number before saving an OBJ. It does not add detail, fill holes, or rebuild missing parts.

The OBJ contains one named object. If the STL has several loose pieces, they stay in the same file; conversion does not join them into one solid shape or give each piece its own name.

The OBJ format can store more than a shape, including links to materials. This tool creates a plain shape file. It does not add colors, surface pictures, or instructions for wrapping those pictures around the model.

Choose how much detail to keep

Under Model Detail, choose the option that fits your next step:

  • Original: keeps all triangles. This is the default and the best choice when you want to keep the existing shape.
  • Balanced: aims for half as many triangles, with small changes to the shape.
  • Simplified: aims for a quarter as many triangles. It allows more change, so small features and curves may lose detail.

Fewer triangles usually mean a smaller OBJ file that is easier to work with. These are targets, not guaranteed amounts. The tool may keep more triangles, or keep the original model, if it cannot reduce the shape within its limits.

After changing the option, click Convert to update the preview, triangle count, and OBJ size. Check small holes, thin edges, and curved areas before saving. Keep your original STL so you can go back to it.

Why is there no MTL file?

An MTL file tells a 3D app which materials to use with an OBJ. This converter does not create one because it exports the shape only. You can open the OBJ without an MTL file.

Add colors or surface pictures in your 3D editor after importing it. If that app saves an MTL file and image files alongside the OBJ, keep them together so the appearance loads correctly next time.

Check the size before you start editing

STL does not say whether its size numbers mean millimeters, inches, or another unit. The converter normally keeps those numbers unchanged. Check a known dimension after opening the OBJ in your editor.

For a very small STL, the tool may ask you to choose:

  • Scale to millimeters: makes the model 1,000 times larger. Use this when the STL was saved in meters but you need millimeter values.
  • Keep original: leaves the size unchanged. Use this if the model is meant to be small or its size is already correct.

For example, a 0.05-meter-wide model becomes 50 millimeters wide with the first choice. That choice does not convert inches. For inch-based files, keep the original here and set the correct size in your 3D editor.

Will the OBJ be easier to edit?

You can edit its points and faces in a 3D editor, but the model still consists of triangles. A hole will not become a simple diameter setting, and a curved edge will not regain its original CAD controls.

A detailed STL may have thousands of small faces. Balanced or Simplified can reduce that number before you open the OBJ in your editor. You may still need to rebuild the areas you want to change.

Even with Original selected, the OBJ may look more angular in another app because of how that app lights the faces. Smoother shading can change its appearance without changing the actual surface.

Check the result and keep working

Open the file in your 3D editor to continue editing. For a quick check of the original shape, use the Free Online STL Viewer.

When your edited model is ready for a slicer that needs STL, use the Free OBJ to STL Converter. If you only need a 3MF version of the original print model, use the Free STL to 3MF Converter directly.