How to use it
- Drop the 3D file you want to convert.
- Pick the output format.
- Check the source units, scale and rotation in the live preview.
- Click Convert and download.
Input and output formats
| Direction | Formats |
|---|---|
| Input | STL, OBJ (+ MTL), GLB / GLTF, 3MF, PLY, FBX, DAE, STEP / STP, IGES |
| Output | STL (binary), STL (ASCII), OBJ, GLB, 3MF, PLY (binary) |
Popular conversions include STL to OBJ for modeling apps, OBJ to STL and GLB to STL for 3D printing, STL to 3MF for modern slicers, and STEP to STL when a CAD part needs to be printed. The output size shows up next to the preview so you can check it before downloading.
You can also drop several files at once, for example an OBJ together with its MTL and texture images, or a GLTF with its .bin buffer. The converter reads them as one model, and warns you when a referenced file is missing so you know why textures may not appear.
Units and axes, handled for you
3D formats disagree about units and which way is up:
| Format | Unit | Up axis |
|---|---|---|
| STL, 3MF, PLY | millimeters (by convention) | Z |
| OBJ | no fixed unit | Y (usually) |
| GLB / GLTF | meters (by the glTF spec) | Y |
| FBX | often centimeters | Y |
The converter guesses the source unit from the format, and you can override it (mm, cm, m or inches). The output is written in millimeters, or in meters for GLB, so a 50 mm part stays 50 mm. When the up axis differs between the source and target formats, Convert axes rotates the model so it doesn't end up lying on its back.
Scale, rotate and center
- Scale in percent: 100% keeps the size, 200% doubles it, 2540% turns a model drawn in inches-as-millimeters into the right size.
- Rotate around X, Y and Z in 90° steps, for example to lay a part on its flattest face before printing.
- Center and place on the build plate moves the model to the middle with its bottom at zero, which is what slicers expect.
The preview updates live in the output orientation, so what you see is what you download.
What is kept and what is lost
STL, 3MF and the PLY output carry geometry only. Textures, colors and materials from OBJ, GLB, FBX or DAE are dropped when you convert to those formats. If you need a colored model for the web or AR, convert to GLB (or OBJ). Animation, rigs and cameras are not converted; only the static mesh is.
STEP and IGES are exact CAD surfaces. They are turned into a triangle mesh in your browser, which is what printers and most 3D tools need. Very small fillets may become slightly faceted.
Binary or ASCII STL?
Binary STL is about five times smaller and is what every slicer reads, so it is the default. ASCII STL is plain text: larger, but you can open it in a text editor, which some older CAM tools and scripts require. Both contain the same triangles.
All conversion happens on your device; the model is never uploaded. To inspect the result, open it in the STL viewer.
Frequently asked questions
How do I convert STL to OBJ?
Drop the STL, choose OBJ as the output format and click Convert. The model is turned to Y-up automatically, as most OBJ tools expect.
Can I convert STEP to STL online?
Yes. Drop the STEP or STP file, pick STL and convert. The CAD surfaces are meshed in your browser; the first time, a 7 MB reader is downloaded.
Why did my converted model lose its colors?
STL, 3MF and PLY output contain geometry only. Choose GLB or OBJ to keep colors and textures.
My model is 25.4 times too small. How do I fix it?
Set the source units to inches, or scale by 2540%. The output will then be correct in millimeters.
Is the converter free and private?
Yes. It is free, needs no account, and your files never leave your browser.
Last updated: November 12, 2026