How do I convert STEP to 3DM online?

Upload your STEP file (.step or .stp) to Marathon OS, choose 3DM as the output format, and download the converted file in seconds — no software installation required.

Why convert STEP to 3DM?

STEP is the standard CAD exchange format. Converting STEP to 3DM produces a Rhino-compatible mesh you can open in Rhinoceros without a STEP import plugin.

What STEP and 3DM file extensions are supported?

This converter accepts .step or .stp input files and outputs .3dm. Upload up to 300 MB per file.

Is the STEP to 3DM converter free?

Files under 5 MB are free to convert and download on Marathon OS. Larger files may require a small fee per conversion.

How is my data stored and secured?

Your files are encrypted during upload, processed securely in the cloud, and automatically deleted after 24 hours.

Do I need any special software or training?

No — upload your STEP file and download 3DM directly in your browser. No plugins or desktop CAD tools required.

Can I convert large STEP models to 3DM?

Yes — Marathon OS is optimized for large and complex CAD models. You can upload files up to 300 MB for STEP to 3DM conversion.

Files under 5 MB free

Free Online STEP to 3DM Converter

Easily convert your .step files to .3dm format using our powerful online 3D CAD converter—no downloads or installations required.

Encrypted uploads

Auto-delete in 24hrs

Up to 300 MB

Drag & drop your 3D file here to convert

or click to browse files

Files under 5 MB convert and download free. Larger files require a small fee per conversion — new file or re-run.

Supported formats: .step

Don't have a file? Try a sample:

Need to preview before converting?

Open your CAD file in the Marathon OS 3D viewer first to inspect geometry, check scale and confirm the model before converting it to another format.

Open CAD Viewer

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Browse CAD modelsExplore 3D models in various formats.Browse 2D technical drawingsFind and download technical drawings.Get CAD design supportConnect with experts for design assistance.

Conversion quality notes (read before converting)

CAD → Mesh (STEP/IGES/BREP → STL/OBJ/PLY/3DM): may lose parametric features; output becomes triangles.
Mesh → CAD (STL/OBJ/PLY → STEP/IGES/BREP): may produce surfaces/approximations depending on engine.
If output looks broken, try converting to STEP first, then to your target format.

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HOW IT WORKS

How to convert STEP to 3DM online

No downloads. No plugins. Works right from your browser.

Upload your STEP file

Drag & drop or browse to select your .step file

Select 3DM as the output format

Choose 3DM as your target CAD format

Convert and download instantly

Download your converted 3DM file in one click

Upload CAD File Open CAD Viewer

Why use Marathon OS 3D CAD File Converter

Lightning-fast conversion

Convert in seconds with our cloud-based engine. No waiting.

No installation required

Works in your browser — no downloads or plugins needed.

Handles large & complex models

Optimized for large and intricate CAD files up to 300 MB.

Secure & private

Encrypted uploads. Files automatically deleted after 24 hours.

Your files, your IP

Full file ownership stays with you. We never share your data.

Available 24/7

Convert files anytime, anywhere — no restrictions.

Privacy and file handling

Encrypted uploads + secure processing

Files are encrypted during upload and processed securely.

Automatic deletion after 24 hours

Uploads are automatically deleted after 24 hours.

File ownership stays with you

You retain full ownership of your files.

STEP

Standard for the Exchange of Product model data is an ISO standard (ISO 10303) used for representing product data in a neutral and portable format for computer-aided design (CAD) and manufacturing applications. It enables the exchange of 3D CAD models, assemblies, and related product data between different software systems.

3DM

3DM is the native file format of Rhinoceros (Rhino), based on the openNURBS toolkit. It stores 3D geometry such as NURBS surfaces, polysurfaces, meshes, and related object data, and is widely used in industrial design, architecture, jewelry, and manufacturing pipelines.

Popular conversions.

CAD Converter Types

STEPBREP

For solid geometry processing

STEPIGES

For cross-platform CAD exchange

STEPOBJ

For rendering and visualization

STEPPLY

For mesh and scan-style export

STEPSTL

For 3D printing and rapid prototyping

STEPOFF

For geometry research workflows

STEP3DM

For Rhino / OpenNURBS workflows

IGESBREP

For solid model processing

IGESSTEP

For modern CAD compatibility

IGESOBJ

For visualization pipelines

IGESPLY

For mesh export from legacy CAD

IGESSTL

For 3D printing from legacy files

IGESOFF

For geometry research workflows

IGES3DM

For Rhino / OpenNURBS workflows

OBJBREP

For solid CAD workflows

OBJIGES

For legacy CAD exchange

OBJSTEP

For CAD editing from mesh files

OBJPLY

For mesh interchange

OBJSTL

For mesh workflows and 3D printing

OBJOFF

For geometry research workflows

OBJ3DM

For Rhino mesh/NURBS handoff

PLYBREP

For solid CAD workflows

PLYIGES

For legacy CAD exchange

PLYOBJ

For rendering and editing

PLYSTEP

For CAD import from scan data

PLYSTL

For 3D printing pipelines

PLYOFF

For geometry research workflows

PLY3DM

For Rhino scan-data workflows

STLBREP

For solid reconstruction workflows

STLIGES

For legacy CAD exchange

STLOBJ

For game engines and 3D rendering

STLPLY

For mesh interchange

STLSTEP

For reverse engineering workflows

STLOFF

For geometry research workflows

STL3DM

For Rhino mesh workflows

OFFBREP

For solid CAD workflows

OFFIGES

For legacy CAD exchange

OFFOBJ

For visualization pipelines

OFFPLY

For mesh interchange

OFFSTL

For 3D printing pipelines

OFFSTEP

For modern CAD import

OFF3DM

For Rhino geometry workflows

BREPSTEP

For CAD/CAM handoff

BREPIGES

For legacy CAD exchange

BREPOBJ

For visualization pipelines

BREPPLY

For mesh export

BREPSTL

For additive manufacturing

BREPOFF

For geometry research workflows

BREP3DM

For Rhino / OpenNURBS workflows

3DMBREP

For solid CAD workflows

3DMIGES

For legacy CAD exchange

3DMOBJ

For visualization pipelines

3DMPLY

For mesh export

3DMSTL

For 3D printing pipelines

3DMOFF

For geometry research workflows

3DMSTEP

Move Rhino models into CAD/CAM

DWGDXF

Convert DWG to DXF for 2D CAD exchange

DXFDWG

Convert DXF to DWG for 2D CAD exchange

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Frequently asked questions

Find answers about converting files with Marathon OS step to 3dm converter.

How do I convert STEP to 3DM online?
Upload your STEP file (.step or .stp) to Marathon OS, choose 3DM as the output format, and download the converted file in seconds — no software installation required.
Why convert STEP to 3DM?
STEP is the standard CAD exchange format. Converting STEP to 3DM produces a Rhino-compatible mesh you can open in Rhinoceros without a STEP import plugin.
What STEP and 3DM file extensions are supported?
This converter accepts .step or .stp input files and outputs .3dm. Upload up to 300 MB per file.
Is the STEP to 3DM converter free?
Files under 5 MB are free to convert and download on Marathon OS. Larger files may require a small fee per conversion.
How is my data stored and secured?
Your files are encrypted during upload, processed securely in the cloud, and automatically deleted after 24 hours.
Do I need any special software or training?
No — upload your STEP file and download 3DM directly in your browser. No plugins or desktop CAD tools required.
Can I convert large STEP models to 3DM?
Yes — Marathon OS is optimized for large and complex CAD models. You can upload files up to 300 MB for STEP to 3DM conversion.

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