Free OBJ to STL Converter
Drop an OBJ file below to save it as a binary STL for 3D printing. Your file is never uploaded.
Your files never leave your browser. Nothing is uploaded.
What are OBJ and STL files?
OBJ, also called Wavefront OBJ, is an old and simple text format for 3D shapes. It lists points and the faces that join them. Almost every 3D app can read and write it, which makes it a common way to move a model between programs.
Blender, Maya, 3ds Max, Rhino, ZBrush, SketchUp Pro, and many scanning apps can export OBJ.
STL is the plain format of 3D printing. It stores a model as a list of triangles and nothing else: no colors, no textures, and no unit. Slicing programs and CAD tools all read it.
STL is what slicers and print services expect. It holds geometry only, and slicers read it as millimeters.
How to convert OBJ to STL
Step 1. Drop your OBJ file on the converter above, or choose it from your device. If the model comes with other files, such as pictures, a .bin, or a .mtl, choose them in the same go.
Step 2. Look at the preview. If the model lies on its side, change the up direction to match your file.
Step 3. Check the unit. OBJ does not say which unit it uses. Choose the unit your model was made in, and the STL file is scaled to millimeters. The size next to the download button changes with it.
Step 4. Press the download button. The STL file is saved to your device, named like your original with .stl at the end.
Printing a model from an OBJ
OBJ is how many modeling and scanning apps hand off a model, and slicers prefer STL. The converter turns the model so Z is up and writes binary STL triangles. Faces with more than three corners are cut into triangles along their outline, so walls with openings keep their holes.
An OBJ does not say which unit it uses, and the STL will be read as millimeters. Choose the unit your model was made in. Blender models are often in meters, and CAD exports in millimeters. The size next to the download button is the size your slicer will show.
What survives the conversion
Shapes. Every face is read, and faces with more than three corners are cut into triangles. Shapes are written as triangles in a binary STL.
Colors and materials. Colors come from the .mtl file when you pick it together with the OBJ. Without it the model is plain. Colors are not kept.
Textures. Pictures named in the .mtl are read when you pick them too. Textures are not kept.
Animation. OBJ cannot hold animation. Animation is not kept, so the model is saved in its first pose.
Units and direction. OBJ does not say which unit it uses. The file is written in millimeters with Z pointing up, which is what slicers expect. A model with several parts is saved as one file.
If something looks wrong
OBJ files from CAD tools can be very large. If yours is over the size limit, export a smaller part.
You do not need the .mtl or the pictures for an STL. Choose the .obj alone.
An OBJ that is only a surface, such as a single wall, has no inside. A printer needs a closed solid.
Check the size shown before you print. A part that is 1000 times too big or too small usually means the unit was wrong.
The converter does not repair holes. A printer needs a closed shape, so check the file in your slicer.
If your browser cannot draw 3D, there is no preview, but the conversion still works.
Your file stays on your device
The converter reads your OBJ file in the browser and writes the STL file there too. Nothing is uploaded, and the page does not load anything the file points to, other than files you choose yourself. The page counts a visit like any other page, but it never sees the file's name or contents.
Questions
Is this OBJ to STL converter free, and is my file uploaded?
It is free, and you do not need an account. Your file is read and converted in your browser and never uploaded, so it stays on your device.
Do I need the .mtl file?
No. An STL holds shapes only, so colors from the .mtl are not used. Choose the .obj alone.
My OBJ is in meters. Which unit do I choose?
Choose meters. The converter then multiplies the numbers by 1000, and your slicer reads the STL in millimeters at the right size. Check the size shown next to the download button.
Which unit and direction does the STL file use?
The file is written in millimeters with Z pointing up, which is what slicers expect. A model with several parts is saved as one file.
How large a file can I convert?
Files up to 150 MB. A very large model may convert slowly on a phone or an older computer, so export only the part you need if it struggles.
More free tools
- Free STL to OBJ ConverterConvert an STL file to OBJ in your browser to open a printable part in modeling and render apps. Free, with no upload and no sign-up.Free, in your browser
- Free OBJ Viewer OnlineOpen an OBJ file in your browser. Turn it, zoom in, and check the triangle count and size. Free, with no upload and no sign-up.Free, in your browser
- Free STL Viewer OnlineOpen an STL file in your browser. Turn it, zoom in, and check the triangle count and size before you print. Free, with no upload and no sign-up.Free, in your browser
- Free OBJ to GLB ConverterConvert an OBJ file to GLB in your browser. Choose the .mtl and pictures with it to keep colors and textures. Free, with no upload.Free, in your browser
- Free GLB to STL ConverterConvert a GLB file to STL for 3D printing in your browser. Scaled to millimeters and stood upright for your slicer. Free, with no upload.Free, in your browser
- Free FBX to STL ConverterConvert an FBX file to STL for 3D printing in your browser. Choose the unit and get a binary STL. Free, with no upload and no sign-up.Free, in your browser
Make it a finished render
Open the studio and add your OBJ file. The studio opens GLB, glTF, OBJ, FBX, STL, 3MF, or DAE files. You pick the angle and describe the finish, and Inkfinish renders that view as a finished image.
Try 3 renders free, no sign-up needed: watermarked, at standard size.
Updated October 2026. Open-source licenses