What the FBX keeps, and what it adds
| In the FBX | |
|---|---|
| Shape | Every triangle, with its corners shared |
| Size | Centimeters, stated in the file, from the unit you choose for the STL |
| Which way up | Y up, with the model standing as it stands on screen |
| Several files | A model for each, named after its file |
| Material | A matte light gray, unless the STL is one of the few with colors: then a model and a material for each color |
| Limit | 5 million triangles, all the files on show together |
| Normals | The flat normals of the STL's triangles, at every corner |
How to convert an STL to FBX
- Drop the STL on this page, or choose it with the button. Binary and ASCII STL both open. It is read in your browser; nothing is uploaded.
- Look at the model and its size. Under Units, choose the unit it was drawn in: millimeters for nearly every STL made for printing.
- Choose Download FBX. The file is named after the STL:
bracket.stlbecomesbracket.fbx.
Size and orientation
FBX states its unit in the file, and every program that reads it scales the model from there. The FBX is written in centimeters, the unit the FBX SDK and Maya write by default, so a part 60 mm long is 6 units long in the file, and a program set in meters reads 0.06 m. The model is stood on Y, the up of the FBX format, as it stands on screen: a program that works with Z up, such as Blender, turns it back on import.
For game engines and animation
FBX is the format game engines, Maya, 3ds Max and Blender exchange models in. An STL has no materials, no texture coordinates and nothing that moves, so the FBX holds the shape alone, in one plain material, ready to be given its look in the program you open it in. For a web page or AR, a GLB is the better file.
Checked in Blender, Godot and the FBX SDK
The FBX of the sample bracket was opened in Blender 5.2.3, in Godot 4.7.2 and in Autodesk’s FBX SDK 2020.3.7, on November 6, 2026. All three read one model of 614 triangles, named bracket, 60 × 30 × 40 mm with Y up: the bracket’s 60 × 40 × 30 mm, standing as it stands here. Its material is the plain light gray. assimp 6.0 reads the same mesh and faces.
The site’s own FBX viewer opens the FBX at the same size. It draws the gray a little darker than Blender does: FBX does not say whether its colors are in linear light, Blender and Godot read them so, and three.js, which the viewer uses, does not.
How the tools are tested lists every converter’s file and what opened it.
Questions
Is my file uploaded?
No. The STL is read and the FBX is written by your own browser. Nothing is sent to a server.
Why does the FBX come out the right size?
An FBX states its unit, and the programs that read it scale it from there. An STL states none. The converter takes the unit you choose under Units, millimeters to begin with, and writes the FBX in centimeters from it, the unit FBX files are written in by default: the sample bracket, 60 mm long, is 6 cm long in the FBX and 60 mm in Blender.
Which way up is the FBX?
Y up, the FBX format's own, which Blender and game engines turn to their own way up on import. An STL stands on Z, and the model is stood on Y as it stands on screen. If it was drawn on its side, choose the other axis in the Views menu: the FBX follows what you see.
What color is the model?
A plain light gray, matte, which most STL files are drawn in, since most have no color: give it the material you need in the program you open the FBX in. A binary STL colored by Materialise Magics or VisCAM keeps its colors, up to 32: the triangles of each color become a model of their own, with a material of that color.
Can I put several STL files into one FBX?
Yes. Drop them together, or drop more on the open model. Each becomes a model of its own in the FBX, named after its file, where its STL put it. Hide any you want left out.
Is the FBX binary or text?
Binary FBX 7.4, the version Blender writes, with its arrays compressed as Blender and Autodesk's FBX SDK compress theirs. Blender, Godot, assimp and the FBX SDK were each given the sample's FBX, and read it.