STL to OBJ converter

Convert an STL file to OBJ for Blender, a game engine or a renderer. Drop the STL, look it over in 3D, and download a clean OBJ with shared vertices, in millimetres.

Open a 3D model

Drop a 3D model hereor click to pick an STL, OBJ, 3MF, PLY, GLB or glTF file (with its .bin or .mtl)

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Size: –
Mesh: –
Watertight: –
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Surface: –
Filament: –

Y is up (stand it up for printing) Close small holes Show triangles

More formats

How to convert STL to OBJ

Drop the .stl file (binary or ASCII) in the box above.
Check the size and units in the facts under the view; change File units or Scale if needed.
Download OBJ. The corners are joined, so the OBJ opens as one connected mesh rather than a pile of loose triangles.

Going the other way? OBJ to STL. Want to edit it? Edit STL online.

Open FlatCad 3D, free, no signup

Questions

Is the OBJ smaller than the STL?

Usually, yes: STL repeats every corner for every triangle, while OBJ stores each corner once and refers to it. A binary STL and its OBJ are often similar in size; an ASCII STL is far bigger.

Which way up is the OBJ?

Z up, in millimetres, the same as the STL. Blender's OBJ import turns Z-up files the right way round when you set Up axis to Z.

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.

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.