Free STL converter
3D files and images to STL

Convert STEP, OBJ, FBX, 3DS, glTF, PLY and IFC models to STL, or turn a PNG or JPG into a 3D relief for printing.

Everything runs in your browser, so no file is uploaded.

Free, no sign-up. Your file stays on your computer. It is opened and converted in this browser tab and is never uploaded to us or anyone else.

File will not convert, or the model needs cleaning up? Our team fixes and converts it for you. Send us the file and we reply with a fixed price. Send the file

  • No upload, no sign-up and no watermark
  • Shows the size, the triangle count and whether the mesh is watertight
  • Also converts STL to STEP, OBJ, GLB and PLY
How it works

How to convert a file to STL

3 steps, and the file never leaves your computer.

1. Add your file

Drop a 3D model on the converter or click to choose it. For an OBJ with materials and textures, select the .obj, .mtl and image files together, or drop them as one .zip file.

2. Check the model

The model opens in a 3D preview that you can rotate and zoom. The panel under it shows the triangle count, the size in millimetres when the file has units, and whether the mesh is watertight.

3. Download the STL

Keep STL selected, or pick STEP, OBJ, GLB or PLY, and click Convert and download. The new file is written in your browser and saved to your downloads folder.

Image to STL

How to turn an image into an STL file

Switch the converter to Image to STL. It reads the brightness of each pixel as a height and builds a solid, printable relief.

Logos, signs and reliefs

With the default setting, dark areas are raised and light areas stay at the base height. A black logo on a white background becomes a raised logo on a flat plate. Transparent areas count as white.

Lithophanes

A lithophane is a thin print that shows the picture when light shines through it. Keep dark areas raised, set the base to 0.8 mm and the relief to 2.2 mm (3 mm in total), and print it standing upright in white filament.

Size and detail

Set the width in millimetres and the depth follows the proportions of the image. More detail points give sharper edges and a bigger file. 200 points across is enough for most prints up to 150 mm wide.

Supported formats

Files it opens and files it saves

The converter opens 18 3D formats and saves 7. CAD formats such as STEP and IGES are turned into triangles at a fine setting, so curved surfaces stay smooth.

STL.stl

The standard file for 3D printing: a mesh of triangles with no colour and no units.

OpensSaves
STEP.step .stp

The CAD exchange format of SolidWorks, Fusion 360, Inventor, Creo, CATIA and Onshape. Saved STEP files are made of flat faces.

OpensSaves
OBJ.obj .mtl

A common mesh format with materials and textures, read by almost every 3D program.

OpensSaves
FBX.fbx

The Autodesk format of 3ds Max and Maya, and of game engines such as Unity and Unreal.

OpensDoes not save
glTF and GLB.gltf .glb

The format for the web, AR and real-time viewers, with materials packed into one file.

OpensSaves
PLY.ply

A mesh format used by 3D scanners and photogrammetry software, often with colour on every point.

OpensSaves
3MF.3mf

The newer 3D printing format of slicers such as PrusaSlicer, Bambu Studio and Cura.

OpensDoes not save
IFC.ifc

The open BIM format exported by Revit, ArchiCAD, Tekla and Vectorworks.

OpensDoes not save
3DM.3dm

The Rhino format, used in architecture, jewellery and product design.

OpensSaves
3DS.3ds

The older 3ds Max format, still common in model libraries.

OpensDoes not save
IGES and BREP.igs .iges .brep

Older CAD exchange formats for surfaces and solids.

OpensDoes not save
DAE, OFF and VRML.dae .off .wrl

Mesh formats from SketchUp exports, research tools and older software. OFF can also be saved.

OpensSaves
Before you print

4 things to check in an STL file

A converted file can be correct and still print badly. These are the first checks a 3D printing service runs.

A watertight mesh

A printable STL must be a closed solid, with no holes and no loose edges. The converter shows Watertight: Yes or No for files up to 400,000 triangles. If it says No, repair the mesh in your slicer, in Microsoft 3D Builder or in Blender before you print.

Units and scale

STL files have no units. STEP and IGES models are converted in millimetres, which is what slicers expect. IFC building models usually arrive in metres. If a model is 10, 25.4 or 1,000 times too big or too small, it was drawn in centimetres, inches or metres: scale it in the slicer.

The triangle count

Curved surfaces are stored as many small flat triangles. Too few, and circles print with visible flat sides. Too many, and the file becomes slow to handle. Most prints need between 50,000 and 1 million triangles.

Binary or ASCII STL

Binary STL is about 5 times smaller than ASCII STL and every slicer reads it, so it is the default. ASCII STL is plain text. Choose it only when another program asks for it.

When a converted file is not enough

What a converter cannot do for you

A converter changes the file format. It cannot add detail that is not in the file, fix a model that was built wrong or turn a drawing into a 3D model. That is modelling work, and it is what we do.

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STL converter FAQ

Questions about converting to STL

Short answers on privacy, formats and file size.

Ask us a question
Is this STL converter free?
Yes. There is no sign-up, no watermark and no limit on how many files you convert. We offer it for free because the people who use it sometimes need a 3D model built or rendered, which is the work we are paid for.
Are my files uploaded to your server?
No. The converter runs in your browser. Your file is read and converted on your own computer and saved straight to your downloads folder. The only thing loaded from the internet is the converter code itself.
How do I convert a STEP file to STL?
Drop the .step or .stp file on the converter, keep STL selected and click Convert and download. The STEP solid is turned into triangles at a fine setting (0.1% of the model size), so curves stay smooth. An assembly is saved as one STL with all of its parts in place.
Can I convert STL to STEP?
Yes. Choose STEP as the output. Each triangle becomes a flat face, and a watertight STL opens in CAD as a solid that you can measure and cut. Curves stay faceted, because an STL file does not contain the original curves. A model with true curves has to be rebuilt; see our 3D modeling service. STEP output is limited to 300,000 triangles.
Can I convert a SketchUp, Revit or SolidWorks file to STL?
Not directly, because these are closed formats that only their own programs can read. Export from the program first: in SketchUp use File > Export > 3D Model, in Revit export IFC, and in SolidWorks save as STEP or STL. Then convert the exported file here.
How big can the file be?
There is no fixed limit. Your computer does the work, so the limit is its memory. Files of a few hundred megabytes usually work on a normal laptop.
Does the STL keep colours and textures?
No. STL stores only the shape. To keep materials and textures, choose OBJ or GLB as the output. To keep the colour of each point from a 3D scan, choose PLY.
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