Files under 5 MB free
10 supported formats
No software installation

Free online 3D CAD file converter

Convert CAD solids, surface models, polygon meshes and 2D drawings between 10 common engineering formats. Choose the file you have and the format required by your CAD, CAM, 3D-printing, visualization or supplier workflow.

Format conversion preserves compatible data. It does not recreate proprietary feature history or information that the destination format cannot store.

Encrypted uploads
Up to 300 MB
Automatically deleted within 7 days

Upload your CAD, mesh or drawing file

Upload a supported file. Marathon OS will detect its format, then show only compatible output options.

Secure

Drag and drop your file here

or choose a file from your computer

Browse files

Maximum file size: 300 MB

Files under 5 MB convert and download free. Larger files use one credit for one completed download, regardless of file size.

No file available? Choose a sample that matches the workflow you want to test.

Pricing

Pay as you go, cheaper by the pack

Files under 5 MB convert and download free. Larger files use one credit for one completed download, regardless of file size. 1 credit downloads any file, any size, and credits never expire.

Starter

3credits

$7.99

$2.66 each

Save 11%

3 downloads of any size. Good for a one-off project.

Pro

5credits

$12.99

$2.60 each

Save 13%

5 downloads of any size. The everyday choice.

★ Most popular

Team

10credits

$19.99

$2.00 each

Save 33%

10 downloads of any size. Best balance of price and volume.

Studio

15credits

$26.99

$1.80 each

Save 40% · best value

15 downloads of any size. Lowest price per file.

Just need one? Pay $2.99 for a single downloadNo subscriptionCredits never expireInvoice on every purchase

Most-used CAD workflows

Start with the exact conversion you need

Go directly to a dedicated route with the input and output already selected.

STEP to STL

Create a triangle mesh for slicing, prototyping and 3D printing.

STL to STEP

Move a triangle mesh into a STEP-compatible CAD exchange workflow without promising recovered feature history.

IGES to STEP

Move legacy surfaces and wireframes into a modern CAD exchange container.

STEP to IGES

Prepare STEP geometry for a supplier or legacy system that requires IGES.

OBJ to STL

Create a standard mesh for slicing and 3D-printing workflows.

OBJ to STEP

Create a STEP-compatible representation from polygon geometry for CAD import and inspection.

3DM to STEP

Move Rhino geometry into a STEP-based CAD or manufacturing handoff.

STEP to 3DM

Prepare STEP geometry for Rhino and OpenNURBS workflows.

DXF to DWG

Move exchange drawings into a DWG-compatible editing workflow.

DWG to DXF

Create an exchange drawing for applications that accept DXF.

Supported formats

CAD, mesh and drawing formats in one converter

Select a destination according to the geometry and information the next application can use.

  • STEP / STP

    STEP / STP

    Neutral CAD exchange for boundary-representation geometry, surfaces, solids, assemblies and product structure.

    Extensions: .step, .stp

    View STEP converters
  • IGES / IGS

    IGES / IGS

    Legacy CAD exchange for curves, wireframes and surface geometry.

    Extensions: .iges, .igs

    View IGES converters
  • STL

    STL

    Triangle-mesh format used for slicing and 3D printing. Standard STL does not define units, materials or feature history.

    Extensions: .stl

    View STL converters
  • OBJ

    OBJ

    Polygon-mesh format that can reference materials and textures through separate files.

    Extensions: .obj

    View OBJ converters
  • PLY

    PLY

    Polygon and scan-data format that can store vertex, face and color attributes.

    Extensions: .ply

    View PLY converters
  • OFF

    OFF

    Compact polygon-geometry format commonly used in research and geometry-processing workflows.

    Extensions: .off

    View OFF converters
  • BREP

    BREP

    Boundary-representation geometry describing faces, edges and vertices.

    Extensions: .brep, .brp

    View BREP converters
  • 3DM

    3DM

    Rhino and OpenNURBS format that can contain NURBS curves, surfaces, solids, meshes and object data.

    Extensions: .3dm

    View 3DM converters
  • DWG

    DWG

    CAD drawing format used for native drawing entities, layers, blocks and annotations.

    Extensions: .dwg

    View DWG converters
  • DXF

    DXF

    Drawing-exchange format used to move supported CAD entities between drafting applications.

    Extensions: .dxf

    View DXF converters

How it works

Convert CAD files online in three steps

No desktop installation or plugin is required to start a conversion.

Upload the source file

Drag and drop a supported CAD, mesh or drawing file up to 300 MB.

Choose a compatible output

Select the format required by the next application. Marathon OS should show only conversion routes supported for the detected input.

Convert, download and inspect

Download the converted file, then verify geometry, units, structure and compatibility in the application used for the next step.

Start a conversion

Read before converting

What different conversion types can change

A file extension is also a data model. When formats represent geometry differently, some information must be translated, approximated or omitted.

CAD solids and surfaces to mesh

STEP, IGES, BREP or 3DM geometry is tessellated into triangles or polygons. Parametric features, exact analytic surfaces, assemblies and product metadata may be lost.

View CAD-to-mesh routes

Mesh to CAD exchange

STL, OBJ, PLY or OFF geometry may become faceted surfaces, a sewn shell or a solid where the mesh is valid. Conversion does not recreate sketches, constraints or native feature history.

View mesh-to-CAD routes

CAD exchange to CAD exchange

Compatible surfaces, solids and topology can be translated, but proprietary features, application metadata, materials and assembly relationships may change.

View CAD exchange routes

DWG and DXF drawing exchange

Layers and common entities may transfer, while fonts, external references, proxy objects, dimensions and application-specific data may require review.

View drawing routes

If the output looks wrong

First verify that the source opens correctly and matches the expected units. Repair invalid geometry before retrying. Do not automatically convert through STEP unless the documented route is known to improve that specific case.

Open CAD viewer

When to use it

Built for common engineering handoffs

Choose a direct conversion when the geometry is usable and the next tool simply requires another supported format.

3D printing

Convert compatible CAD geometry to STL or another supported mesh for slicing and prototyping.

Supplier handoff

Provide a neutral file format that a manufacturer, vendor or client can open.

CAD inspection

Create a format that can be opened in a browser viewer or the receiving CAD application for review.

Rhino and visualization

Move compatible geometry between 3DM, STEP, OBJ and other supported workflows.

Legacy migration

Translate IGES or DXF data for a newer exchange or editing workflow.

Mesh-to-CAD handoff

Package mesh geometry for CAD import or inspection when a clean parametric reconstruction is not required.

All conversion routes

Find the exact input and output pair

Choose the format you have, then open the dedicated converter for the result you need. Every dedicated page should arrive with both formats already selected.

Convert from STEP

STEP to BREP

For solid geometry processing

STEP to IGES

For cross-platform CAD exchange

STEP to OBJ

For rendering and visualization

STEP to PLY

For mesh and scan-style export

STEP to STL

For 3D printing and rapid prototyping

STEP to OFF

For geometry research workflows

STEP to 3DM

For Rhino / OpenNURBS workflows

Convert from IGES

IGES to BREP

For solid model processing

IGES to STEP

For modern CAD compatibility

IGES to OBJ

For visualization pipelines

IGES to PLY

For mesh export from legacy CAD

IGES to STL

For 3D printing from legacy files

IGES to OFF

For geometry research workflows

IGES to 3DM

For Rhino / OpenNURBS workflows

Convert from STL

STL to BREP

For solid reconstruction workflows

STL to IGES

For legacy CAD exchange

STL to OBJ

For game engines and 3D rendering

STL to PLY

For mesh interchange

STL to STEP

For reverse engineering workflows

STL to OFF

For geometry research workflows

STL to 3DM

For Rhino mesh workflows

Convert from OBJ

OBJ to BREP

For solid CAD workflows

OBJ to IGES

For legacy CAD exchange

OBJ to STEP

For CAD editing from mesh files

OBJ to PLY

For mesh interchange

OBJ to STL

For mesh workflows and 3D printing

OBJ to OFF

For geometry research workflows

OBJ to 3DM

For Rhino mesh/NURBS handoff

Convert from PLY

PLY to BREP

For solid CAD workflows

PLY to IGES

For legacy CAD exchange

PLY to OBJ

For rendering and editing

PLY to STEP

For CAD import from scan data

PLY to STL

For 3D printing pipelines

PLY to OFF

For geometry research workflows

PLY to 3DM

For Rhino scan-data workflows

Convert from OFF

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

Convert from BREP

BREP to STEP

For CAD/CAM handoff

BREP to IGES

For legacy CAD exchange

BREP to OBJ

For visualization pipelines

BREP to PLY

For mesh export

BREP to STL

For additive manufacturing

BREP to OFF

For geometry research workflows

BREP to 3DM

For Rhino / OpenNURBS workflows

Convert from 3DM

3DM to BREP

For solid CAD workflows

3DM to IGES

For legacy CAD exchange

3DM to OBJ

For visualization pipelines

3DM to PLY

For mesh export

3DM to STL

For 3D printing pipelines

3DM to OFF

For geometry research workflows

3DM to STEP

Move Rhino models into CAD/CAM

Convert from DWG

DWG to DXF

Convert DWG to DXF for 2D CAD exchange

Convert from DXF

DXF to DWG

Convert DXF to DWG for 2D CAD exchange

Continue the workflow after conversion

Inspect the result, find a starting model, open a technical drawing or request specialist help when conversion is not enough.

Open a CAD file

Inspect geometry, scale and orientation before or after conversion.

Open CAD viewer

Browse CAD models

Find an existing engineering model that may shorten the design process.

Browse 3D models

Browse technical drawings

Review available 2D drawing resources for quoting, documentation and manufacturing.

Browse 2D drawings

Create 2D drawings from STEP

Turn a supported STEP or STP model into a multi-view drawing set when a format conversion is not enough.

Create 2D drawings

Hire a CAD designer

Request repair, remodeling, tolerances or a production-ready native file.

Get CAD design support

Frequently asked questions

Frequently asked questions about CAD file conversion

Answers about supported formats, conversion quality, pricing, file limits and privacy.

  • What can I convert with the Marathon OS CAD converter?

    Marathon OS supports direct routes between selected STEP, STP, IGES, IGS, STL, OBJ, PLY, OFF, BREP, 3DM, DWG and DXF files. Available outputs depend on the detected input format.

  • Is the online CAD converter free?

    Files under 5 MB can be converted and downloaded free. Larger files use one credit for one completed download.

  • What is the maximum file size?

    You can upload a supported file up to 300 MB. Processing time and output size depend on the source format, geometry and model complexity.

  • Will conversion preserve every CAD feature?

    No. Compatible geometry can transfer, but native feature history, proprietary metadata, materials, textures, assemblies, fonts or drawing objects may change or be omitted when the destination format cannot represent them.

  • Can a mesh be converted into a parametric CAD model?

    A mesh can be placed into a STEP, IGES or BREP-compatible representation, but automatic format conversion does not reconstruct the original sketches, constraints or feature tree. A native rebuild is required when those features matter.

  • Do I need CAD software to convert a file?

    No desktop CAD software is required to upload and convert a supported file. You should still open the result in the target application or viewer to verify it before production use.

  • How are uploaded files handled?

    Files are transferred securely, processed privately, excluded from the public CAD library and automatically deleted within 7 days. You retain ownership of the uploaded design.

  • What should I do if the converted file is incorrect?

    Confirm the source file opens correctly, verify its unit and repair invalid geometry. If the task requires new features, tolerances or a clean native model, use a CAD design service rather than repeatedly changing formats.

When conversion is not enough

Use the converter when the geometry is correct and only the file format needs to change. Work with a vetted CAD designer when the model is damaged, incomplete, missing tolerances or needs a production-ready native rebuild.

Hire a CAD designerStart a conversion

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