Have a 3MF model but need an STL? Open your file, choose the parts and download a geometry-only copy at the right size.
STL stores coordinates, not a unit label. Import the result in millimeters.
Open a real 3MF example, change the selection and inspect the exported geometry.
Frame, lid and knob in one project. Export the whole set or isolate one piece.
3 parts · millimeter unitsInspect a continuous ring and its open center after conversion.
1 part · curved surfaceThe 1-inch source becomes 25.4 mm without guessing the scale.
1 in → 25.4 mmA .3mf is a model package that can also carry a print setup. An .stl is the model's triangle surface. Choose what you want to do next.
Use this 3MF to STL converter when a mesh editor, print service or older workflow asks for an STL. You already need a 3MF containing model geometry; a photo or G-code file cannot replace it.
Open the enclosure example and isolate Lid in the part list. The preview and STL contain just that piece. The selected part retains its placement, so re-center it in your slicer if necessary.
If your slicer already opens the project and you want its colors, material assignments or print settings, converting to STL offers no benefit for that task. Open the 3MF in compatible software instead.
Drop a 3MF that contains triangle meshes. Your browser reads its units, parts and build placement.
Use the part list to isolate a piece or include several. Keep the original size, or set a new longest side.
Rotate the STL, check its dimensions and download. Use the STL checker, then inspect layers in your slicer.
3MF can hold an entire print project. STL is a triangle surface file. Keep your original 3MF if you need to return to the project.
| In your source | In the STL |
|---|---|
| Triangle geometry | Selected mesh surfaces |
| Units and placement | Coordinates converted to millimeters; transforms applied |
| Separate parts | Multiple shells in one STL; no boolean union |
| Colors, textures and materials | Not included in standard binary STL |
| Supports, printer and slicer settings | Project settings and toolpaths are not exported |
Carry the model's surface into a workflow that expects STL. Set printer, supports and material again in the destination slicer.
Choose a lid, insert or bracket without sending the entire project. Its coordinate placement remains intact.
Inspect a geometry-only copy independently of slicer settings. Keep 3MF for a multicolor or fully configured print project.
Mesh-containing projects can work when they use core meshes and supported production references. Sliced-only or G-code-only packages cannot be reconstructed into the original surface. Proprietary required extensions are rejected.
Export only the parts you need. The local tool accepts 25 MB compressed, 64 MB unpacked, 12 MB of model XML, 200,000 triangles and 100 mesh parts, including repeated instances.
Source millimeters, centimeters, inches and other core 3MF units convert to millimeter coordinates. Conversion does not close holes, thicken walls or make overlapping parts a single solid.
Start with a project that still contains the model. A file extension alone does not tell you whether a package contains editable meshes or only sliced output.
Open the source in its original app and confirm the objects are visible in the model workspace, not only in a layer or toolpath preview.
Try the mesh-containing 3MF here. If a required extension is unsupported, use the original app's model export to obtain a standard mesh file.
Select the parts, convert and import the STL into your destination slicer. Configure material, supports and printer settings there.
Compatibility depends on the contents and extensions of each project; sliced-only packages cannot restore the original model.
If the destination already accepts your 3MF and you need its project data, keep using the original file.
If it specifically needs STL, download the converted selection and open it as a model in millimeters.
Compare X, Y and Z dimensions with this preview. Arrange the parts on the bed and inspect the sliced layers.
Conversion preserves source placement. A part away from the origin may need arranging on the print bed.
Start with the file or setting that caused the problem. Repeating the same upload cannot recover missing geometry.
| What you see | What to check | What to do next |
|---|---|---|
| No geometry found | The package may contain only sliced output, not triangle meshes. | Return to the original model or unsliced project and export its geometry. G-code cannot supply the original surface. |
| Unsupported extension or missing part | The project depends on unsupported features or incomplete internal references. | Open it in the app that created it and export a self-contained mesh. Do not delete referenced files from the package. |
| A 1-inch part becomes tiny | The destination app may interpret STL coordinates using the wrong unit. | Use millimeters on import. The one-inch example should read 25.4 × 25.4 × 25.4 mm. |
| Some pieces are absent | Only selected parts are exported; hidden internal geometry can also be hard to see. | Review the part list, select all if needed, and rotate the preview before exporting again. |
| The STL is larger than the 3MF | 3MF compresses its contents; binary STL stores triangles without ZIP compression. | Check that the expected parts are present. A larger file alone is not an error; avoid repeated unnecessary instances. |
| The slicer still reports a mesh issue | Format conversion does not repair open surfaces or fuse intersecting solids. | Run the STL checker, repair the original geometry if needed, and inspect the new result before printing. |
Use this checklist on your exported file. These checks help catch transfer mistakes; they do not certify a physical print.
Open the STL checkerChoose your 3MF, select the parts and check the preview. Keep original size or set a longest side, then download the binary STL. Import it in millimeters.
Yes. The conversion runs locally in your browser, with no account, upload or generation credits. Fomrix AI model generation is a separate credit-based feature.
STL does not contain unit metadata. This tool exports millimeter coordinates; choose millimeters in the importing application. A one-inch source should measure 25.4 mm, not 1 mm.
No. This STL contains geometry only. Colors, textures, material assignments, printer profiles and slicing instructions stay in your original 3MF.
No. A project must contain supported mesh geometry and resolvable internal references. Sliced-only packages and unsupported required extensions are reported instead of producing an incomplete STL.
No. The selected surfaces share one STL file and keep their placement. They remain separate shells, and intersecting surfaces are not fused. Use a boolean operation in a mesh editor when you need a union.
