# 3MF to STL converter The 3MF to STL converter unpacks a 3MF in your browser and writes its triangles as a binary STL for any slicer. The unit the 3MF declares is applied, so the part keeps its real size in millimetres; colors, materials and print settings are left behind, and nothing is uploaded. > Canonical: https://ai3d.studio/3mf-to-stl ## 3MF to STL in numbers ### 6 units understood A 3MF may declare micron, millimetre, centimetre, inch, foot or metre; the converter scales from that unit to millimetres. ### 50 bytes per triangle The STL written is binary: an 80-byte header and a 4-byte triangle count come first, then 50 bytes for every triangle. ### 4 height presets Choose 28, 50, 100 or 180 mm tall, or Original size to keep the dimensions the 3MF states. ### 250 MB per file The largest 3MF the page opens; the package is unzipped inside the browser tab. ## What survives 3MF to STL The geometry crosses; everything a slicer added around it stays in the 3MF. ### Every triangle in the build Kept ### Real-world size Kept ### Z-up orientation Kept ### Colors and painted filaments Dropped ### Plates and print settings Dropped ## What a 3MF holds that an STL cannot Why the same part needs a different file once it leaves the 3MF. ### A package, not a mesh A 3MF is a ZIP holding the model as XML, a content-types list, relationships and, when a slicer wrote it, that slicer's own settings files. ### A unit written in The model element says which unit its coordinates use. An STL has no unit field, so the converter writes millimetres, the unit slicers assume for STL. ### Vertices listed once In a 3MF triangles point into a shared vertex list. A binary STL repeats all three corners for every triangle and is not compressed, so the STL is usually the larger file. ## Convert a 3MF to STL in three actions STL is already selected as the output on this page. ### Drop the 3MF Pick or drop the .3mf file, up to 250 MB. The page reads the unit it declares and shows the part's size. ### Keep the size or set a height Leave Original size, or choose 28, 50, 100 or 180 mm to scale the part to that height. ### Press Convert to STL The binary .stl saves to your device, with the height in its file name when you chose one. ## Limits of 3MF to STL conversion An STL is the simplest print format, so some of the 3MF cannot come along. ### A multicolor print loses its colors A painted 3MF becomes one plain STL. For a multicolor print, keep the 3MF, or rebuild colors from a texture with the vertex-color tool. ### Every object goes into one file All meshes in the build are written to a single STL; cut it afterwards if the parts must print separately. ### Faults are copied, not fixed Open edges and inside-out faces in the 3MF reach the STL unchanged; run STL repair before slicing if the part is not a closed solid. ## What to open around the 3MF to STL step The reverse conversion, the repair and split steps that usually follow, and the multicolor route. ### [STL to 3MF](https://ai3d.studio/stl-to-3mf) Go back the other way, with the millimetre unit written into a 3MF. ### [Repair the STL](https://ai3d.studio/repair-3d-model-for-printing) Close holes and check the part is a closed solid before slicing. ### [Cut it into parts](https://ai3d.studio/split-3d-model-for-printing) Split one merged STL into pieces that fit the bed. ### [Quick color 3MF](https://ai3d.studio/texture-to-vertex-color) Turn a textured model into a multicolor 3MF with 2 to 16 filament colors. ### [Make a part to print](https://ai3d.studio/ai-3d-model-generator) No 3MF yet? The AI 3D model generator builds a model from a picture, a prompt or a sketch, ready to save as STL. ## Questions about 3MF to STL Answers about units, colors and slicer projects. ### How do I convert a 3MF to STL? Drop the .3mf on the converter, keep Original size or pick a print height, and press Convert to STL. The converter applies the unit the 3MF declares and saves a binary STL in millimetres. ### Does 3MF to STL keep colors? No. STL stores triangles only, so base materials, color groups and painted filament assignments are dropped. Keep the 3MF when the print needs several colors. ### Will my part change size when I convert a 3MF to STL? Not unless you pick a print height. A 3MF names its unit, from micron to metre, and the converter writes the same physical size in millimetres. ### Why is the STL larger than the 3MF? A 3MF is a compressed ZIP whose triangles share one vertex list. A binary STL repeats every corner and is not compressed, so the same part takes more bytes. ### What happens to plates, supports and print settings? Plates, supports and print settings are not part of an STL. Only the meshes in the 3MF's build are written, merged into one file; slicer settings and supports stay in the original 3MF. ### Who uses 3MF to STL, and for what? Makers whose slicer, print service or CAD tool accepts only STL, and people sharing a part on sites that ask for STL. A multicolor print is better kept as 3MF. ### Is 3MF to STL conversion free and private? Yes. Nothing leaves your device: the 3MF is unzipped and written as STL inside the tab, with no account and no credits. ### Can I use what 3MF to STL makes commercially? Every plan, the free tier included, lets you use what 3MF to STL makes commercially: the outputs generated for you are yours. ### How does 3MF to STL compare, and what alternatives fit a different workflow? 3MF to STL: Convert 3MF to STL free in your browser: the unit the 3MF declares is applied, the part stays Z-up in millimetres and colors are dropped. Nothing is uploaded. Related options are AI 3D model editor: AI 3D model editor for a mesh you already have: upload GLB, OBJ, FBX or STL up to 200 MB, then retexture, remesh, rig or segment it. From 25 credits a tool, GLB to OBJ: Convert GLB to OBJ free in your browser: a ZIP with the .obj, an .mtl and base-color PNG textures. Roughness, metalness and animation are not carried, STL to 3MF: Convert STL to 3MF free in your browser: the same triangles with shared vertices and the millimetre unit written into the package. Nothing is uploaded, OBJ to GLB: Convert OBJ to GLB free in your browser: pick the .obj with its .mtl and textures and get one self-contained file. Nothing is uploaded, GLB to STL: Convert GLB to STL free in your browser: stood upright Z-up, written in millimetres, scaled to 28, 50, 100 or 180 mm. Color is dropped; nothing is uploaded, and GLB to USDZ: Convert GLB to USDZ free in your browser: PBR materials and textures written for Apple AR Quick Look, in metres, Y-up. Animation is not carried. Choose by the required input, delivered output, controls, limits, current availability, and credit cost; the related-tools section links each canonical page. ## Convert a 3MF to STL now Drop the .3mf above and save the STL. ## Related tools ### [AI 3D model editor](https://ai3d.studio/ai-3d-model-editor) ### [GLB to OBJ](https://ai3d.studio/glb-to-obj) ### [STL to 3MF](https://ai3d.studio/stl-to-3mf) ### [OBJ to GLB](https://ai3d.studio/obj-to-glb) ### [GLB to STL](https://ai3d.studio/glb-to-stl) ### [GLB to USDZ](https://ai3d.studio/glb-to-usdz) _Last updated October 8, 2026_