# 3DM to STL converter

> Convert Rhino .3dm files to STL, 3MF or OBJ in your browser without a Rhino licence. Meshes, cached render meshes, SubD and blocks are converted in millimetres. Free, no upload.

Source: https://freestlviewer.com/3dm-to-stl/  
Updated: October 22, 2026

Convert Rhino .3dm files to STL without Rhino. Meshes, saved render meshes, SubD and blocks are converted in your browser — nothing is uploaded. The tool is interactive: open https://freestlviewer.com/3dm-to-stl/ and drop a file onto the page.

## Who needs this

Jewellers sending a ring to a printing or casting service, makers who got a
Rhino file from a designer, students without a licence at home: the `.3dm`
is the source, but the printer workflow needs STL or 3MF.

## How it works

The converter loads **rhino3dm**, McNeel's WebAssembly build of openNURBS
(about 2.7 MB, once), and collects everything that can be meshed:

| In the 3DM | In the STL |
| --- | --- |
| Mesh objects | Converted as they are |
| Polysurfaces, extrusions | From Rhino's cached render meshes |
| SubD | Meshed from the subdivided control net |
| Blocks | Expanded at every placement |
| Curves, points, dimensions, text | Not converted |

The result is merged into one mesh in millimetres.

## Getting the best mesh from Rhino

The quality of polysurface conversion is the quality of Rhino's render mesh.
For printing, the default render mesh can be coarse on small curved details. If
you have Rhino, set a finer custom render mesh (Document Properties → Mesh)
before saving — or use Rhino's own export to STL with a fine tolerance. If you
do not, this converter gives you the best mesh the file contains.

## Before printing or casting

Check the summary's watertightness line. Jewellery models built from separate
surfaces, or with intersecting parts, may need a Boolean union in Rhino before
they print as one solid.

## On a phone

3DM conversion works in a phone browser. The Mes3D app for iPhone, iPad, Mac and
Android opens 3DM files, measures them and exports STL, OBJ or 3MF.

## Frequently asked questions

### How do I convert a 3DM file to STL without Rhino?

Drop the .3dm onto this page and click Convert and download with STL selected. It is read with McNeel's openNURBS library in your browser and written as STL in millimetres.

### Why are some objects missing from the STL?

Polysurfaces and NURBS surfaces are converted from the render meshes Rhino caches in the file. If the file was saved with SaveSmall or without shading, those meshes are missing. Open it in Rhino, shade the viewport and save normally — or ask the sender to.

### Can I keep the layer colours?

Yes, choose 3MF instead of STL. Object and layer display colours are carried over to the 3MF.

### Is the STL the right size?

Yes, when the 3DM has its unit system set, which Rhino files normally do. The geometry is converted to millimetres.