Convert STL to OBJ
Convert STL to OBJ in your browser. The conversion runs on this page and the file never leaves your computer.
Result
Before you convert: what this keeps and what it destroys
Preserved
- The geometry, triangle for triangle
- Overall dimensions and proportions
- Watertightness, where the input is watertight
Destroyed
- A recorded unit: OBJ stores none
↺ the reverse: OBJ → STL · about .stl · about .obj · just view it instead
Why people convert STL to OBJ
Usually a step on the way into a rendering or modelling tool, since almost every 3D application ever written reads OBJ.
The geometry transfers exactly, because both formats are plain triangle meshes. OBJ adds object names, so if the STL held several disjoint bodies they can at least be labelled. Neither format has a unit, so the numbers pass through unchanged.
What you get
You get a plain-text OBJ file you can open in an editor containing the same triangles the STL file described. No geometry is added, removed or approximated: mesh-to-mesh conversion is a change of container, and this site's tests check that the triangle count comes out identical.
Not carried across by this conversion: a recorded unit.
The conversion runs in your browser. Your file stays on your computer and is not uploaded.
What to check afterwards
- STL carries no unit. The numbers in the file are just numbers, so the conversion assumes millimetres. Check the overall dimensions of the result before you commit to machining or printing it. A file exported from a package set to inches will be 25.4 times out.
- The output keeps supported geometry and object names. The writer applies part transforms to the coordinates, without retaining the original transform hierarchy. It does not write material colours, texture coordinates or a companion material file.
If you need something this conversion cannot give you
If the unit has to be unambiguous, convert to 3MF instead. It records the unit in the file, so nobody downstream has to assume millimetres and nobody has to scale by 25.4 after the fact.
Going the other way
Convert OBJ back to STL. The reverse conversion also works with mesh geometry. It does not reconstruct exact CAD surfaces. Material data and part structure lost in either direction cannot be restored by converting back. Keep the original file for later edits.
How we know this conversion works
This pair was checked against 9 files from the test corpus on 2026-09-04. Each run parses its own output back in and compares the bounding box, the triangle count and, for closed solids, the volume against the input.
A pair that fails those checks doesn't get a page. That's why this site lists 120 conversions and not the several hundred a format-times-format grid would suggest.