Convert GRO to 3MF (Free)
Also converts STL, OBJ, GLB, PLY, USDZ, FBX from the same file.
Runs in your browser. No upload, no signup, nothing to install.
Also from Innerscene: Circadian Lab, a free lighting calculator for room illuminance, melanopic EML, and glare.
How to convert GRO to 3MF
- 1
Open your .gro file
Drag it onto the viewer above, or click "Open a GRO File". Files up to 200 MB open directly; the parse runs in a worker so the page stays responsive.
- 2
Click Download 3MF
Once the file is open, the Download 3MF button sits at the bottom right of the viewer. The Export menu in the toolbar has every other format.
- 3
Download
The .3mf is written in the browser and saved straight to your downloads folder. No queue, no email, no watermark.
What survives the conversion
A file conversion is a translation, and formats do not carry the same things. Here is exactly what moves from GRO into 3MF, and what does not.
| Geometry | Kept | Both formats store triangle meshes, so the shape transfers directly. |
|---|---|---|
| Colors and materials | Reduced | GRO can hold per-vertex color and 3MF holds one color per object, so materials are flattened to that. |
| Layers and structure | Reduced | 3MF has named objects but no layers, so each layer becomes a named part instead. |
| Units and scale | Reduced | GRO coordinates are in ångströms, and the export treats one ångström as one meter: a protein 50 Å across arrives 50 meters across. Scale the model on import to the size you want. |
| Lines and points | Dropped | 3MF geometry is manifold mesh only, so line work and point clouds are skipped. |
What the 3MF writer emits: An OPC package in millimeters, Z-up, with each mesh as its own named object carrying a basematerials color, placed by a build item.
The source: GROMACS structure (GRO) (.gro)
A GROMACS structure converted from nanometres to ångströms: proteins as a cartoon of their chains, other molecules as ball and stick, water, hydrogens and space filling on layers of their own, and a rectangular simulation box drawn as the unit cell. Bonds are worked out from covalent radii.
The target: 3D Manufacturing Format (.3mf)
The modern replacement for STL: named parts, per-object color, and units that are actually in the file.
Opens in: PrusaSlicer, Bambu Studio, Cura, Windows 3D Builder, Fusion 360.
Your file never leaves your computer
Both the GRO parser and the 3MF writer are JavaScript and WebAssembly running in your own browser tab. There is no upload step, no server-side conversion queue, and no copy of your file anywhere but your machine. That matters for drawings under NDA, for client work, and for anything you would not email to a stranger.
Free to Use, No Signup
There are no accounts and no watermarks on this converter. If it saved you time, the one thing we ask is a mention: a post, a link from your blog or course page, or a reply to someone asking how to open a file.
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Hear about new formats
Occasional emails when the viewer learns a new format or gets a new tool.
Frequently asked questions
▶Is this GRO to 3MF converter free?
Yes. No signup, no watermark, no per-file limit and no paid tier. Innerscene.
▶Is my GRO file uploaded anywhere?
No. The file is read with the browser file API and converted in the same tab. Nothing is sent to a server unless you explicitly click Share, which is a separate, opt-in feature.
▶Will my colors and materials survive the 3MF export?
GRO can hold per-vertex color and 3MF holds one color per object, so materials are flattened to that.
▶Do layers and named parts carry into the 3MF file?
3MF has named objects but no layers, so each layer becomes a named part instead.
▶Will the 3MF open at the right size?
GRO coordinates are in ångströms, and the export treats one ångström as one meter: a protein 50 Å across arrives 50 meters across. Scale the model on import to the size you want.
▶How large a GRO file can I convert?
Up to 200 MB, and the ceiling adapts to how much memory your device reports. The conversion runs on your own hardware, so a desktop with plenty of RAM will handle more than a phone.
▶Can I convert 3MF back to GRO?
Not here. We read GRO and write 3MF, but not the reverse. the universal 3D viewer
▶Which browsers does it work in?
Chrome, Edge, Firefox and Safari, on Windows, macOS, Linux, iOS and Android. No plugin and no extension.
Convert GRO to something else
Convert something else to 3MF
Or start from the universal 3D viewer.