3MF to STL Converter
Downloaded a model as a .3mf project and need a plain .stl for another slicer, a print service or a repair tool? Convert it here and keep the geometry at the right scale.
3D Model Converter
or drop STL, OBJ, MTL … files here ·
Max 95 MB per file· Up to 20 files· Deleted after 30 minutes
Files are processed on our servers and deleted after 30 minutes.
STL and OBJ store no units. If a part shows up 10× or 25.4× too small or too big in the slicer, the units were read wrong — set them here.
Blender, CAD programs and slicers use Z-up; glTF, Unity and most game engines use Y-up. Switch it if the model lies on its side after import.
Used when converting STEP or IGES solids to a mesh. Fine gives smooth curves but larger files; coarse is enough for quick previews.
Only used for PNG, JPG or SVG input. Relief raises dark areas; a lithophane is a thin panel that shows the photo when lit from behind; extrude turns a logo or SVG outline into a flat solid shape.
Width of the printed model; the height follows the image's aspect ratio.
Maximum raised height for a relief or lithophane, or the thickness of an extruded shape. Lithophanes usually use 2–3 mm.
Solid plate under the relief so the print holds together. 0 means no base.
How to use this tool
- 1
Upload the .3mf file
Add one 3MF or up to 20, 95 MB each. Project files saved by PrusaSlicer, Bambu Studio, Cura or Windows 3D Builder all work.
- 2
Keep millimeters and binary
Convert to is STL with File encoding Binary and Model units in millimeters, which every slicer expects. Turn on Merge into one mesh only if the parts should become a single object.
- 3
Convert to STL
Press Convert to STL and download. Open the file in your slicer and check the dimensions against the original.
How do I convert 3MF to STL?
Upload the .3mf file, keep STL in millimeters and press Convert to STL. The triangle mesh of each object is written to a binary STL; colors, materials and slicer settings are left out because STL cannot store them.
3MF and STL: a project file versus a triangle list
The 3MF Consortium, founded in 2015 by Microsoft with Autodesk, HP, Dassault Systèmes, Shapeways and others, designed 3MF to replace STL in 3D printing. A 3MF file is a ZIP package following Open Packaging Conventions. The model sits inside as XML, with an explicit unit attribute that defaults to millimeters, and the format adds colors, materials, multiple objects and build plates. Slicers such as PrusaSlicer and Bambu Studio save whole projects as 3MF, adding their own settings files in a Metadata folder.
STL is much older. 3D Systems defined it in 1987 for its stereolithography machines, and it holds one thing: a list of triangles with a normal each. There is no unit, no color, no object name. Because almost every program ever written for 3D printing reads it, STL is still what many tools, older slicers and print-on-demand forms ask for. If the download came as a ZIP of several parts instead, ZIP to STL converts the whole archive in one go.
What 3MF to STL keeps and what it drops
Kept
- Every triangle of every object
- Size, written in millimeters
- Separate parts, unless you merge them
- Holes, overhangs and fine detail
Dropped
- Colors, painted regions and textures
- Material and filament assignments
- Plates, bed positions and supports
- Print settings, modifiers and thumbnails
50 bytesper triangle in a binary STL
Check the STL before slicing
- Compare one known dimension, such as the base width listed on the model page, with what the slicer shows.
- Count the objects: a multi-part print should arrive as the same number of parts.
- Reapply supports and brims in the new slicer; none of them were carried over.
- For multi-material models, assign a filament to each part again.
- If the slicer reports errors, run its repair function; the 3MF specification requires closed meshes, but a model edited later may not be.
- Keep the original 3MF, which still holds the colors and settings the STL cannot.
3MF and STL format facts
3MF
3D Manufacturing Format
3MF is an open 3D printing format released by the 3MF Consortium, founded by Microsoft and industry partners, in 2015. It stores mesh geometry together with units, colours, materials, multiple objects and print settings in a compressed ZIP package. Slicers such as PrusaSlicer, Bambu Studio and Cura use 3MF as their project format. Many general 3D modelling and CAD tools still prefer STL or OBJ.
- Compression
- –
- Transparency
- –
- Animation
- No
- Introduced
- 2015 · 3MF Consortium
STL
STL mesh
STL (stereolithography) is a 3D mesh format created by 3D Systems in 1987. It describes only the surface geometry of an object as a list of triangles, without colour, materials, units or scene information. Its simplicity makes it the default input for 3D printing slicers such as Cura and PrusaSlicer. Curved surfaces are approximated by many flat triangles, so smooth models can produce very large files.
- Compression
- –
- Transparency
- –
- Animation
- No
- Introduced
- 1987 · 3D Systems
People convert 3MF to STL because many slicers, print services and mesh tools still accept only STL, while modern model sites and slicers such as Bambu Studio hand out 3MF project files.
3MF to STL questions
Can I look inside a 3MF file without a slicer?
Yes. A 3MF is a ZIP archive, so renaming a copy from .3mf to .zip lets any unzip tool open it; how to unzip files on any device covers phones and computers. Inside you will find the model as XML under a 3D folder, plus thumbnails and, in slicer projects, the settings files.
Will the multi-color painting from my 3MF survive in the STL?
No. STL has no field for color, so painted regions and filament assignments are dropped. To print in several colors elsewhere, keep Merge into one mesh off so separately modeled parts stay separate, then assign filaments per part in the new slicer.
Does the STL keep the plate layout of a Bambu Studio project?
No. Plates, positions on the bed, supports and modifiers are slicer data, not geometry. The STL holds the model shapes only, and the new slicer arranges them on its own bed.
Why is my STL larger than the 3MF it came from?
3MF stores each vertex once and is ZIP-compressed. Binary STL writes three full corner coordinates for every triangle with no compression, so the same mesh commonly takes several times the space.
Should I send a print service 3MF or STL?
Send what the service lists. Many accept both, and 3MF is safer because it states its units. If a form only lists STL, convert here and mention in the order that the model is in millimeters.
The model is 25.4 times too small after conversion. What happened?
The 3MF was declared in inches, or the target program assumed inches. Convert again with Model units set to in, or scale by 2540% in the slicer, and compare a known dimension.
- OBJ to STL ConverterConvert OBJ models from Blender, ZBrush or a scan into binary STL for 3D printing. Quads are triangulated, parts merged and the scale fixed to millimeters.
- STEP to STL ConverterConvert STEP or STP files to STL for Cura, PrusaSlicer and Bambu Studio. Pick coarse, normal or fine mesh detail and get a binary STL in millimeters.
- ZIP to STL ConverterUpload a ZIP from Thingiverse, Printables or a CAD export and get STL files back. OBJ, 3MF and STEP inside are converted; each part stays a separate STL.
- STL to OBJ ConverterConvert STL to OBJ for Unity, texturing tools and other 3D apps that expect OBJ. Shared vertices, readable text and the same triangles, in seconds.
- PNG to STL ConverterConvert a PNG to STL as a lithophane panel: brightness becomes thickness, 0.8 to 3.2 mm, ready to print and light from behind. Relief and logo modes too.
- Image to STL ConverterTurn a JPG, PNG, WebP or BMP image into a printable STL: a raised relief, a backlit lithophane or a flat extruded shape. Set width, depth and base in mm.