What is Marathon OS 3D CAD File Converter?

A browser-based tool for converting common CAD, mesh, and 2D drawing formats without installing desktop software.

Which file formats are supported?

STEP (.step, .stp), IGES (.igs, .iges), STL (.stl), PLY (.ply), OFF (.off), BREP (.brp, .brep), OBJ (.obj), 3DM (.3dm), DWG (.dwg), and DXF (.dxf).

Is the converter free to use?

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

What is the maximum file size?

You can upload files up to 300 MB.

How is my data stored and secured?

Your files are encrypted during upload, processed securely, and automatically deleted after 7 days.

Do I need any special software or training?

No—just upload your file and convert it directly in your browser. No downloads or plugins required.

Can I convert large and complex CAD models?

Yes—Marathon OS is optimized for large and complex engineering models, with uploads supported up to 300 MB.

Files under 5 MB free

10 supported formats

No software installation

Free Online 3D CAD File Converter

Convert CAD, mesh and drawing files between common engineering formats in your browser. Upload securely and convert STEP, STL, IGES, OBJ, PLY, OFF, BREP, 3DM, DWG and DXF files without installing desktop CAD software.

Encrypted uploads

Auto-delete in 7 days

Up to 300 MB

Upload your CAD or 3D file

We'll detect the input format. Choose the output you need.

Secure

Drag and drop your 3D file here

or choose a file from your computer

Browse files

Maximum file size: 300 MB

Input format

Auto-detect

Output format

Files under 5 MB convert and download free. For larger files, 1 credit = one download of any size — buy a pack.

Don't have a file? Try a sample:

Most used CAD workflows

Start with a popular conversion

Jump directly into the format pair used most often for printing, CAD exchange, Rhino, mesh editing and 2D drawing workflows.

STEP to STL

For 3D printing and rapid prototyping

STEP to 3DM

For Rhino / OpenNURBS workflows

3DM to STEP

Move Rhino models into CAD/CAM

STL to STEP

For reverse engineering workflows

DXF to DWG

Convert DXF to DWG for 2D CAD exchange.

DWG to DXF

Convert DWG to DXF for 2D CAD exchange.

STEP to IGES

For cross-platform CAD exchange

IGES to STEP

For modern CAD compatibility

OBJ to STL

Convert OBJ to STL for mesh workflows and 3D printing.

STL to OBJ

For game engines and 3D rendering

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

Supported formats

CAD, mesh and drawing formats in one tool

Choose a format based on whether you need editable engineering geometry, lightweight visualization, scan data, 3D printing or 2D drafting exchange.

STEPCAD / mechanical
Parametric solids and assemblies
.step, .stp
IGESCAD exchange
Legacy surfaces and wireframes
.igs, .iges
STL3D printing
Triangular surface meshes
.stl
OBJRendering / mesh
Mesh geometry with material references
.obj
PLYScanning / research
Polygon and scan data
.ply
OFFResearch / geometry
Simple polygon geometry
.off
BREPSolid modeling
Boundary representation solids
.brp, .brep
3DMRhino modeling
Rhino / OpenNURBS models
.3dm
DWG2D drawing
Native 2D CAD drawings
.dwg
DXFCAD exchange
Interchangeable 2D CAD drawings
.dxf

How it works

Convert CAD files online in three steps

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

Upload your CAD file

Drag and drop a supported file or browse from your computer.

Choose the output format

Select STEP, IGES, STL, OBJ, PLY, OFF, BREP, 3DM, DWG or DXF.

Convert and download

Process the model securely and download the converted file in one click.

Read before converting

Conversion quality notes

CAD → Mesh

STEP, IGES or BREP to STL, OBJ, PLY or 3DM may lose parametric features because the output becomes triangles or polygons.

Mesh → CAD

STL, OBJ or PLY to STEP, IGES or BREP may create reconstructed surfaces or approximations, depending on the engine and model quality.

Broken output

If the target file looks incorrect, try converting to STEP first and then convert STEP to the final format.

When to use it

Built for real engineering handoffs

3D printing

Turn CAD or mesh files into slicer-compatible formats.

Supplier handoff

Send a file format your manufacturer or vendor can open.

CAD review

Prepare models for browser preview, markup or design review.

Prototyping

Move between engineering and mesh formats during iteration.

Design collaboration

Exchange files between Rhino, CAD, render and scan tools.

Legacy migration

Convert older IGES or DXF files into modern workflows.

Privacy and file handling

Secure conversion without giving up file ownership

Files are encrypted during upload, processed securely and removed automatically after 7 days.

Encrypted upload

Secure transfer and processing for every supported format.

7-day deletion

Uploaded and converted files are removed automatically.

You retain ownership

Your CAD files and intellectual property remain yours.

Popular conversions

Browse every CAD converter type

Filter by source format or search for the exact conversion you need. The directory stays compact while preserving internal links to every converter page.

All STEP IGES OBJ PLY STL OFF BREP 3DM DWG DXF

OFF to BREP

For solid CAD workflows

OFF to IGES

For legacy CAD exchange

OFF to OBJ

For visualization pipelines

OFF to PLY

For mesh interchange

OFF to STL

For 3D printing pipelines

OFF to STEP

For modern CAD import

OFF to 3DM

For Rhino geometry workflows

Showing 7 converters

Continue your CAD workflow

Explore Marathon OS CAD resources

Preview a model, find an existing file, open a technical drawing, or get expert support when conversion is not enough.

Open CAD Viewer

Inspect geometry, scale and orientation before or after conversion.

Browse CAD models

Explore downloadable engineering models across multiple categories.

Browse 2D drawings

Find technical drawings for components, assemblies and manufacturing.

Get CAD design support

Work with vetted designers on production-ready engineering files.

Explore 3D printing files

Find ready-to-use models for prototyping and additive manufacturing.

View all engineering tools

Access viewers, drawing pipelines and related browser-based utilities.

Frequently asked questions

Everything to know before converting

Quick answers about formats, pricing, file limits, conversion quality and privacy.

What is Marathon OS 3D CAD File Converter?
A browser-based tool for converting common CAD, mesh, and 2D drawing formats without installing desktop software.
Which file formats are supported?
STEP (.step, .stp), IGES (.igs, .iges), STL (.stl), PLY (.ply), OFF (.off), BREP (.brp, .brep), OBJ (.obj), 3DM (.3dm), DWG (.dwg), and DXF (.dxf).
Is the converter free to use?
Files under 5 MB are free to convert and download. Larger files may require a small fee per conversion.
What is the maximum file size?
You can upload files up to 300 MB.
How is my data stored and secured?
Your files are encrypted during upload, processed securely, and automatically deleted after 7 days.
Do I need any special software or training?
No—just upload your file and convert it directly in your browser. No downloads or plugins required.
Can I convert large and complex CAD models?
Yes—Marathon OS is optimized for large and complex engineering models, with uploads supported up to 300 MB.