OBJ to STL converter
Convert an OBJ file to STL for your slicer. Drop the OBJ, check it in 3D, and download the STL. Models from Blender and 3D sites are stood upright, units are set, small holes are closed, and nothing is uploaded.
Open a 3D model
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- Size
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- Mesh
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- Watertight
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- Volume
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- Surface
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- Filament
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More formats
How to convert OBJ to STL
Drop the .obj file in the box above (its .mtl isn't needed).
Check it stands right. Y is up is ticked for OBJ files; untick it if the model now lies on its side.
Check the size. If the file was in centimetres, metres or inches, pick it in File units, or type a Scale.
Download STL (or 3MF, which keeps the units for Bambu Studio, PrusaSlicer, Orca and Cura).
Going the other way? STL to OBJ. Just looking? The STL viewer.
Open FlatCad 3D, free, no signup
Questions
Why does my OBJ come in lying down?
OBJ files from Blender, Maya and most 3D sites are Y-up; printers are Z-up. Y is up is ticked for OBJ files so the model stands the right way; untick it if your OBJ was already Z-up.
Are colours and textures kept?
No: STL has no colours, so only the shape is converted. The .mtl and textures are not needed.
Why is my model the wrong size?
STL and OBJ files store bare numbers without units. The tool reads the units when the file says (3MF, glTF, or a note in the header) and otherwise guesses from the size; if it guessed wrong, pick File units, or type a Scale. Downloads are always in millimetres.
The STL isn't watertight. What now?
Many OBJ files are made for rendering, not printing: open surfaces, faces stored twice. Close small holes fixes simple gaps. For a model of many loose parts, Edit in FlatCad 3D joins and mends the pieces when it imports.
Is my file uploaded?
No. The model is read and converted in your browser; it never leaves your computer, so private or client parts stay private.
How big a file can it open?
Files up to about 250 MB, several million triangles, in a desktop browser. Phones manage smaller files.