STL to OBJ Converter

Turn STL files into OBJ for Blender, Maya, ZBrush or a game engine. Every triangle is kept, corners are welded into shared vertices, and you choose which way is up.

  • Files stay on your device
  • Free, no sign-up
  • Units and up axis handled
  • Batch and .zip

Drop an STL file to convert

One file, many, or a .zip

In: STL · STEP · IGES · OBJ · 3MF · GLB · glTF · PLY · FBX · DAE · 3DS · AMF · VRML · ZIP

Converted on your device. Nothing is uploaded.

    How to convert STL to OBJ

    1. Drop your STL files

      Drop one or more .stl files, binary or ASCII, or a .zip of them.

    2. Check the preview

      The model appears at the size and orientation it will have. Fix the file units, up axis or size under Size, units and orientation if needed.

    3. Choose OBJ options

      Keep materials on to get a .zip with the .obj, its .mtl and textures. Pick the up axis: Y for Blender and game engines, Z for slicers and CAD.

    4. Convert and download

      One file downloads straight away. A batch gives a download per file and one .zip of all of them.

    What carries over from STL to OBJ

    Worked out from what each format can store and what this converter writes. Nothing is changed silently: the preview shows the size and orientation before you download.

    Geometry Every triangle is kept at full precision.
    Color STL has no color to carry. The OBJ comes out uncolored.
    Units OBJ stores no units. The numbers stay in the unit the STL was read in (millimetres); you can change that in the options.
    Orientation Kept the way the STL had it. Switch to Y up (Blender, game engines) or Z up (slicers, CAD) in the options.
    Objects Each part stays a separate object or mesh.

    STL to OBJ: what actually happens

    STL stores nothing but triangles, so STL to OBJ is lossless: every triangle comes across at full precision. The converter also welds the loose STL corners into shared vertices, the way OBJ readers expect, which makes the OBJ editable as one connected surface and usually smaller than an ASCII STL.

    OBJ has no units, so a 40 mm part becomes 40 units. Blender treats a unit as a metre, so scale by 0.001 on import if real size matters. Orientation is the other catch: STL is Z up, and Blender's OBJ importer assumes Y up. Choose Y up in the OBJ options when the file is going to Blender, and keep Z up when it is going back to a slicer.

    STL at a glance

    Stereolithography (Standard Triangle Language) · .stl

    Stores
    Loose triangles: three corners and a normal each, binary or ASCII
    Color
    None in the standard
    Units
    None written; slicers assume millimetres
    Up axis
    Z, the slicer convention
    File size
    50 bytes per triangle in binary, about 5 times that as ASCII
    Opens in
    Every slicer, CAD tool and 3D app

    Created by 3D Systems in 1987 for the first stereolithography printers, STL is still the format every slicer and print service accepts. It describes a surface as a list of independent triangles, with no shared vertices, units, colors or scene structure.

    Open STL files in the viewer

    OBJ at a glance

    Wavefront OBJ · .obj

    Stores
    Vertices, faces (triangles, quads, n-gons), UVs and normals as text
    Color
    Materials and textures in a separate .mtl file; vertex colors as an unofficial extension
    Units
    None, the numbers are bare
    Up axis
    Y by convention (Blender, Maya, most 3D apps)
    File size
    Text: about a binary STL's size for bare geometry, up to twice that with UVs and normals
    Opens in
    Blender, Maya, 3ds Max, ZBrush, Cinema 4D, game engines, most slicers

    OBJ came out of Wavefront Technologies' animation software and became the plain-text lingua franca of 3D. The geometry is in the .obj; colors and texture references live in a companion .mtl file, which is why OBJs so often arrive grey.

    Open OBJ files in the viewer

    Tips for STL to OBJ

    Going to Blender?

    Choose Y up. Blender's importer turns Y up into its own Z up, so the model arrives standing.

    Flat facets

    STL normals are per facet. The OBJ carries none, so Blender's Shade Auto Smooth works without fighting it.

    Want color?

    STL has none to carry. Paint it in Blender, or paint filament colors in the 3D model painter and export 3MF.

    STL to OBJ FAQ

    Does converting STL to OBJ lose quality?
    No. Both store triangles, so every triangle is kept at full float precision. Only duplicate corners are merged into shared vertices.

    Why is my OBJ lying on its back in Blender?
    STL is Z up and Blender's OBJ importer assumes Y up. Convert again with Y up, or set Up Axis to Z in Blender's import options.

    Can I convert many STL files to OBJ at once?
    Yes. Drop them all, or a .zip, convert once, and download each OBJ or a single .zip.

    Is the converter free? Are there limits?
    Free, with no sign-up, watermark or file count limit. Batches and files of a few hundred MB work on most laptops; the only limit is your device's memory.

    Are my files uploaded?
    No. Files are read and written by JavaScript and WebAssembly in your browser and never sent to PrintPal. The STEP and IGES reader is the only extra download, once, from a public CDN.