FBX to STL Converter

Turn an FBX model into an STL for 3D printing, right in your browser. FBX files store their own unit scale, and many are in centimetres, so a plain copy of the numbers opens ten times too small in a slicer. This converter reads the unit scale from the file and writes the STL in millimetres, so it opens at the size it was modelled. All meshes are merged into one STL with their positions, rotations and scales applied, and turned Z-up, as printers expect. For a rigged character you can print the rest pose or any frame of an animation. Every STL is read back straight after it is written, and the page shows the triangle count, the size and whether the mesh is watertight. Nothing is uploaded.

100% private — everything runs in your browser. Everything runs in your browser; your FBX files are never uploaded.

How to convert an FBX to STL

1. Drop an FBX file on the box, or click Try a sample.
2. Check the size line and the file details. If the size looks wrong, choose the FBX units yourself.
3. For a rigged model with animations, choose the rest pose or a frame of an animation to print.
4. Download the STL (binary), or the ASCII STL if your software needs text.

What you can use it for

• Print a game asset or character from an FBX
• Get a model from an asset store into a slicer at its real size
• Print a pose from an animation, such as a jump or a wave
• Check the size and watertightness of an FBX before printing
• Merge every part of an FBX scene into one print file
• Turn a Y-up 3D app model into a Z-up print file

What changes from FBX to STL

	FBX	STL from this converter
Shape	Meshes in a scene tree, each with its own position, rotation and scale	One mesh of triangles, with every transform applied
Units	Stored in the file (UnitScaleFactor, centimetres per unit)	Millimetres, from the FBX unit scale (or the unit you choose)
Up direction	Stored in the file (Y-up from most 3D apps, some Z-up)	Z-up for printing, or Y-up if you choose
Rig and animation	Bones, skin weights, animation clips	One shape: the rest pose, or a frame you pick
Textures, materials	Embedded or separate image files, materials	None (STL has no colour or texture)
Polygons	Triangles, quads and larger polygons	Triangles only (larger polygons are split)

Units and the size of the STL

Units stored in the FBX	UnitScaleFactor	1 unit in the STL	A 10-unit cube in the STL
millimetres	0.1	1 mm	10 mm
centimetres	1	10 mm	100 mm
inches	2.54	25.4 mm	254 mm
metres	100	1000 mm	10000 mm

The FBX unit scale is the number of centimetres in one unit of the file, so a file in millimetres stores 0.1, centimetres 1, inches 2.54 and metres 100. A file with no unit stored is read as centimetres. The STL is written in millimetres, the unit slicers assume.

What the sample gives

Shape	Triangles	STL size	File	Watertight
Rest pose	20	200 × 20 × 20 mm	1084 bytes	Yes
“Bend” at 0.5 s	20	177.8 × 20 × 87.8 mm	1084 bytes	Yes
“Bend” at 1 s (end)	20	110 × 20 × 110 mm	1084 bytes	Yes

Computed by the converter’s own code and the same three.js FBX loader the page uses, from its Try a sample file: our own 7936-byte binary FBX 7.4 of a 20 cm bar in centimetres with 2 bones and one 1-second animation that bends the second bone by 90 degrees.

Next steps

Check the STL in 3D in the STL viewer, or price the print with the 3D Print Cost Calculator. Have an OBJ or GLB instead? Use OBJ to STL or GLB to STL. For a print file with units built in, try STL to 3MF.

Sources

Sources: The National Archives (UK) PRONOM: FBX (Filmbox) Binary, fmt/1009; The National Archives (UK) PRONOM: FBX (Filmbox) Text, fmt/1010; Autodesk FBX SDK reference: FbxSystemUnit (scale factor relative to centimetres); Library of Congress: STL (STereoLithography) File Format Family; three.js r186 FBXLoader source (binary FBX 6400+, ASCII FBX 7000+).

Not affiliated with Autodesk.

Frequently asked questions

Is this FBX to STL converter free?

Yes. There is no sign-up, no watermark and no limit on how many files you convert. The conversion runs in your browser, so your FBX never leaves your device.

Why is my STL ten times too small or too big?

FBX files keep a unit scale (UnitScaleFactor, in centimetres per unit), and STL files have no units at all. A converter that copies the numbers makes a centimetre model ten times too small in a slicer that reads millimetres. This one applies the unit scale and writes millimetres. If the file’s unit is wrong, choose the FBX units yourself.

What happens to textures, colours and materials?

STL stores only the shape (triangles), so textures, colours and materials are not in the STL. The FBX does not need its texture files for this conversion.

What about rigged characters and animations?

The STL holds one shape. By default it is the rest pose, the shape as modelled before any animation. To print a pose, choose A frame of an animation, pick the animation and move the time slider; the bones are applied to the mesh at that moment.

Are all parts merged?

Yes. Every mesh in the FBX goes into one STL, with its position, rotation and scale in the scene applied, so the parts stay where they were. Point clouds, lines, cameras and lights are left out and listed.

Why Z-up?

3D printing and CAD software treat Z as up, and most FBX files from 3D apps and game engines are Y-up. The STL is turned so the model stands upright on the build plate. Choose Y-up to keep the scene’s direction.

Is the STL watertight?

The page checks the mesh after writing: closed with no open or non-manifold edges means watertight. Game and character models are often made of separate, open pieces (eyes, hair cards, clothing), which slicers usually handle, but a watertight mesh prints most reliably.

Which FBX versions work?

Binary FBX from version 6.4 and ASCII FBX from version 7.0, which covers files from current 3D apps and asset stores (most are binary FBX 7.4 or 7.5+). Older files are refused with a message naming their version; open them in a 3D app and export again as FBX 7.4 or newer.

Is my FBX uploaded?

No. The FBX is read and turned into STL by JavaScript in your browser, so it never leaves your device. There is no sign-up, no watermark and no limit on the number of files.