Convert OFF to 3MF
Upload an OFF mesh and get back a 3MF package that PrusaSlicer, Orca Slicer, Bambu Studio and Cura open directly. The one thing to watch: nothing rescales your coordinates, so whatever numbers are in the OFF are written into the 3MF as millimeters.
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Why convert OFF to 3MF
OFF (Object File Format) comes from the Geomview and academic mesh world. It is a plain text file: the word OFF, a line with the vertex, face and edge counts, then a block of coordinates and a block of face indices. That simplicity is why research code, CGAL, MeshLab and shape-benchmark datasets hand it out, and also why almost nothing on the 3D printing side reads it. Slicers, print services and Windows 3D viewers expect STL or 3MF, so an OFF model has to be re-written before it can go on a build plate.
On MiConvert the job runs on our servers, not in your browser. A small Python program loads your OFF with trimesh, recomputes face winding so triangles face outward consistently, and writes a 3MF package straight away. There is no Blender step and no intermediate GLB in this pair, which matters for one practical reason: the model comes out standing the same way it was authored, with no 90-degree flip to correct after import.
What survives is the mesh: vertex positions and faces, written as the triangles a 3MF mesh stores. Everything else does not. Our 3MF holds one object with one mesh and declares its unit as millimeter; it carries no color, no per-face RGB an OFF file may have included, no materials, no multiple plates, no supports and no print settings. The coordinate numbers are untouched, so an OFF authored in meters or inches will look wrong on the plate until you rescale it there. This is the conversion for people handed a mesh by research tooling who now want to print it or send it to a print service, and for pipelines that have moved from STL to 3MF because slicers open 3MF projects natively.
How to convert OFF to 3MF
- Check the OFF first. It should be the text form starting with OFF or a similar header, and the counts on the second line should match the vertex and face blocks that follow. It also needs faces: a 3MF mesh can only store triangles, so an OFF with vertices and no faces has nothing to write and the job fails instead of giving you a usable part.
- Decide what the coordinates mean. Nothing in the pipeline converts units, so a cube of size 50 in the OFF becomes 50 mm in the 3MF. If the mesh was built in meters or inches, plan to rescale after import.
- Upload the .off file. Guests can send up to 50 MB per file, a free account raises that to 100 MB, Plus 200 MB and Pro 1 GB. You can queue up to 10 files in one batch on the free tiers; each one is converted separately into its own 3MF.
- Let the conversion run on our servers: trimesh parses the mesh, fixes the normals, and exports the 3MF package.
- Download the result, named after your file with a .3mf extension. The download link stays valid for about four hours.
- Open it in your slicer and check the size on the plate. If the OFF was in meters, scale by 100,000%; if it was in inches, 2,540%. Then assign filament, color or supports in the slicer, since none of that can come from an OFF file.
What this converter does
- Direct trimesh export with no Blender or GLB round trip, so the mesh keeps the orientation it had in the OFF file instead of arriving on its back.
- Face winding is recalculated during conversion, which removes inconsistently flipped triangles that often come out of research exporters.
- The 3MF is written as a standard package with its unit declared as millimeter, which slicers read without an import dialog.
- Geometry goes through trimesh without decimation or smoothing; polygon faces are split into the triangles a 3MF mesh stores.
- Batch uploads of up to 10 files per request, each producing a separate 3MF named after the source file. No account is required for files up to 50 MB.
- If the file cannot be parsed, the job fails with a read error ("Could not read this 3D file") instead of returning a broken download.
Video Tutorial
OFF → 3MF in seconds! Free online converter at MiConvert.com 🔗 https://miconvert.com/en/off-to-3mf?utm_source=youtube&utm_medium=social&utm_campaign=off-to-3mf Quick steps: Upload → Convert → Downl
Frequently asked questions
Will colors or materials from my OFF file come through?
No. The 3MF we write is geometry only: one object, one mesh, no color, no material definitions and no texture. OFF files that include per-vertex or per-face RGB lose that information here. Assign colors, filaments or materials in your slicer after import.
Why is my model the wrong size in the slicer?
Because no step converts units. The coordinates from the OFF are written unchanged and the 3MF labels them millimeters. A model authored in meters shows up 1,000 times too small (scale by 100,000%), and an inch model needs 2,540%. OFF has no unit field, so there is nothing we can read to do this for you.
Does the model come out rotated?
Not on this pair. OFF to 3MF is written directly by trimesh, so Z stays Z and the model is upright. You only need to re-orient it if you want a different print orientation.
Does the converter repair the mesh or make it watertight?
No. There is no repair step, so holes, non-manifold edges and self-intersections pass through. The only cleanup is recomputing face winding so normals point outward consistently. For real repair, use MeshLab, Blender's 3D Print Toolbox or your slicer's own fix tool.
Can I merge several OFF files into one 3MF with multiple parts?
No. Each uploaded file is converted on its own into a single-object 3MF, even when you upload several at once. To build a multi-part plate, convert the files individually and arrange them in your slicer, which can save that arrangement as its own 3MF project.
The conversion failed with a read error. What now?
"Could not read this 3D file" usually means the OFF is truncated, the header counts disagree with the data, or the file is really another format with an .off extension. Re-export it and confirm it opens in MeshLab first.
What are the size limits, and what about files over 1 GB?
50 MB per file as a guest, 100 MB with a free account, 200 MB on Plus and 1 GB on Pro. 3D conversions are also eligible for the pay-once large-file option for files over 1 GB and up to 40 GB; it needs a signed-in account and delivers the result by email with a link valid for five days.
What happens to my file after the conversion?
Everything is processed on our servers over HTTPS. Your uploaded OFF is deleted as soon as the job finishes, and the converted 3MF plus its download link are removed automatically about four hours after completion. File names, sizes and outcomes are logged for operations, and signed-in accounts keep a conversion history entry; the files themselves are never listed publicly.