OBJ to STL Converter

Turn OBJ polygon geometry into an STL mesh for software that accepts STL. Inspect the converted shape online before paying for the full-quality download.

OBJ and STL represent meshes differently

OBJ is a text-based geometry format that can describe vertices and polygon faces. It may also refer to material descriptions and image textures stored separately. STL represents a surface using triangular facets and is widely accepted by 3D printing and mesh workflows. Converting OBJ to STL produces a triangle surface representation rather than a native CAD solid.

This conversion is appropriate when a slicer, printer preparation tool, or another application needs STL input. Any non-triangular polygon faces in an OBJ need to be represented as triangles in the output. OBJ appearance references such as MTL materials and textures are not part of ordinary STL geometry, so they are not retained as STL color or texture data.

How to convert OBJ to STL

Select an OBJ file up to 50MB and upload it. StlFixTool checks that the contents contain OBJ geometry and processes the mesh. A filename ending in .obj is not enough by itself: a file that does not contain valid geometry may fail to load.

Once conversion finishes, inspect the 3D preview. Orbit and zoom to examine the overall model, and check orientation and scale as represented. The online preview is limited to at most 30,000 triangles and is provided for inspection; it is not the full-quality STL file.

If the preview meets your needs, pay $2.99 once to download the full-quality STL. Paddle processes the one-time payment. No account or subscription is required, and you are not charged simply for uploading or previewing. Unpaid files are deleted within 60 minutes.

Materials, units, and output expectations

OBJ workflows often use companion MTL and image files for appearance. This converter's STL output is mesh geometry; it does not preserve texture maps or material appearance. If visual materials are important, retain the original OBJ and associated assets in an application that supports them.

OBJ coordinate values do not guarantee a shared unit convention across applications, and STL does not provide reliable unit metadata. The mesh's geometric coordinates are carried through the conversion, but a receiving application may interpret the dimensions differently. Measure the output and select the intended units when importing it.

Check the mesh before printing

Converting a mesh format does not make a model watertight or repair defects automatically. An OBJ may contain open boundaries, intersecting faces, isolated components, or inconsistent orientation. These conditions can affect slicing even when a 3D viewer can display the shape.

Use your slicer's analysis and preview to confirm that the STL is interpreted as expected. Look for missing layers, unexpected infill, disconnected pieces, or scale errors. If the source has defects, the STL Repair tool can attempt supported cleanup; compare its before-and-after information because repair may alter geometry.

Limits and troubleshooting

A malformed OBJ, missing or invalid vertex and face data, a file larger than 50MB, or geometry the loader cannot process can prevent conversion. If the OBJ depends on external files, keep them with the original workflow even though they do not become STL material data. An OBJ that opens in one application may still use features outside another application's support.

STL is a triangle mesh, not a native CAD format. If you need editable CAD surfaces or design history, keep the original CAD source or use a deliberate reverse-engineering process. After download, verify the STL in the exact software and process where it will be used.

Frequently asked questions