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Free 3D converter

Convert OBJ to STL

Drop a OBJ file and download it as STL, scaled and set on the build plate. The conversion runs in your browser, so the file never leaves your device. It keeps the exact shape and a real size in millimetres.

Free, no sign-up, and your file stays on your device.

Drop a OBJ file here

Converted to STL in your browser. Nothing is uploaded.

GLB, glTF, OBJ, STL, PLY, FBX or 3MF, up to 300 MB. Add .mtl, .bin and texture files alongside.

What carries over from OBJ to STL

Checked against what the converter writes, not just what the formats allow.
Shape (triangles)
Kept exactly
UV coordinates
Dropped: STL can't store it
Colour texture
Dropped: STL can't store it
PBR maps (roughness, metalness, normal)
Not in OBJ
Vertex colours
Dropped: STL can't store it
Animation
Not in OBJ
Separate parts
Dropped: STL can't store it
Size and units
OBJ has no units, so 1 unit is written as 1 mm unless you set a height.
Up direction
Turned Z up and set flat on the build plate.

How to convert OBJ to STL

  1. Add your OBJ

    Drop the OBJ file, with its textures and .mtl if it has separate ones.

  2. Check the preview

    Turn the model, check its triangle count, and set the height you want to print in millimetres.

  3. Download the STL

    The .stl is written in a second or two for most models.

When to convert OBJ to STL

  • To 3D print it

    Every slicer reads STL. The OBJ becomes a plain list of triangles, sized in millimetres and ready to slice.

  • To send it to a print service

    Print bureaus and online quote tools ask for STL more than anything else.

The two formats

OBJ

Wavefront OBJ

OBJ is the plain-text mesh format Wavefront Technologies introduced in the late 1980s. It stores vertices, UVs, normals and faces; materials and texture maps live in a companion .mtl file.

Usually comes from
older asset libraries, CAD and DCC exports, and photogrammetry apps
Opens in
almost every 3D app (Blender, Maya, 3ds Max, Cinema 4D, ZBrush), Unity and Roblox Studio natively, and every major slicer
Units
None recorded
Up axis
Not recorded (usually Y up)

STL

Stereolithography

STL was created by 3D Systems in 1987 for its stereolithography printers. It stores a surface as a list of triangles and nothing else: no colour, textures or units.

Usually comes from
print libraries such as Printables and Thingiverse, CAD exports and 3D scanners
Opens in
every slicer (Bambu Studio, PrusaSlicer, OrcaSlicer, UltiMaker Cura and others) and most 3D apps
Units
None recorded (read as millimetres by slicers)
Up axis
Z up by convention

Questions

Something else? Ask us and a person will answer.

Is this OBJ to STL converter free?

Yes. There is no account, watermark or limit on conversions. It accepts files up to 300 MB; how large a model your browser can handle depends on your device's memory.

Is my file uploaded?

No. The conversion runs in your browser with the open-source three.js loaders and exporters, so your OBJ never leaves your device.

Why is my STL the wrong size in the slicer?

The converter shows the output size in millimetres before you download. Set a height to scale it, or keep the original size.

Will colours and textures be kept in the STL?

No. STL stores only triangles. For a full-colour print, keep the OBJ and colour it in your slicer, or export to OBJ with its texture.

Is the model watertight and printable?

The converter keeps the shape exactly; it doesn't repair it. Slicers fix small holes automatically. For meshes with many open edges, run them through your slicer's repair or Blender's 3D Print Toolbox first.

My OBJ has an .mtl file and textures. How do I include them?

Drop or select the .obj, .mtl and texture files together. The converter matches them by file name.

Can I make a 3D model from a photo instead?

Yes. PhotoGenius turns a photo or a text prompt into a textured GLB with Rodin Gen-2.5, Rodin Gen-2.5 Fast, Tripo H3.1, TRELLIS.2, Rodin Gen-2 or Hunyuan3D 3.1, which you can then convert here. See Image to 3D model.

Turn a photo into a 3D model

Rodin Gen-2.5, Rodin Gen-2.5 Fast, Tripo H3.1, TRELLIS.2, Rodin Gen-2 or Hunyuan3D 3.1 builds a textured GLB from one image. The price shows before you run it.