Browser-based conversion
Use the converter without installing desktop software to move from IGES to BREP.
Free under 5 MBIGES → BREPNo software installation
Convert IGES
to BREP online
Convert an IGES (.iges or .igs) CAD model into BREP (.brep) for Open CASCADE geometry processing and topology-based CAD workflows. The converter translates compatible curves, surfaces, solids and topology while preserving engineering geometry wherever the destination format supports it.
Encrypted uploads Files up to 300 MB Deleted after 7 days
Upload your IGES file
Choose one file to begin the conversion.
Drag and drop your 3D file here
or choose a file from your computer
Browse filesMaximum file size: 300 MB
Files under 5 MB convert and download free. Larger files require a small fee per conversion, including a new file or re-run.
Don't have a file? Try a sample:
Built for boundary representation
Translate curves, trimmed surfaces and wireframes into the faces, edges, vertices and solid topology used by BREP.
Ready for the next workflow
Open the result in OpenCascade and solid-modelling CAD systems for review, editing or production.
Private file handling
Converted models are not added to the public CAD library and are removed after processing.
Continue your CAD workflow
Explore Marathon
OS CAD resources
Preview a model before conversion, find an existing engineering file, open a 2D drawing, or get specialist help when a source mesh needs to be rebuilt.
Browse CAD modelsSearch ready-to-use engineering and 3D-printing files across the Marathon OS library.Browse 2D technical drawingsExplore PDF, SVG and DXF drawing resources for engineering review and documentation.Get CAD design supportWork with a vetted designer when the model needs repair, remodelling or a production-ready native file.
Simple conversion workflow
How to convert IGES to BREP online
Move from IGES model to BREP solid in three clear steps.
Upload your IGES file
Drag and drop the .iges file into the converter or choose it from your device. Files up to 300 MB are supported.
Use BREP as the output
This page is preconfigured for IGES-to-BREP conversion, so you do not need to search through target formats.
Download and inspect the BREP
Download the result and open it in your preferred compatible application to confirm its geometry and scale.
Format behaviour
What changes when
IGES is converted to BREP?
IGES and BREP describe geometry differently. Conversion preserves compatible shape and topology while translating or omitting format-specific data.
Normally retained
- Overall model shape
- Compatible geometry
- Model orientation
- Supported topology and layers
May not be retained
- Format-specific metadata
- Unsupported materials or textures
- Application-specific features
- Data without a target-format equivalent
IGES modelIGESBREP solidBREPKeep the original IGES file as the source of truth and inspect the converted BREP file before downstream production use.
Format comparison
IGES versus BREP
Choose the output according to what the next stage of your workflow needs.
| Feature | IGES IGES | BREP BREP |
|---|---|---|
| Main purpose | Legacy CAD exchange and surface-based engineering workflows | Solid modelling, topology and CAD kernel workflows |
| Geometry | Curves, trimmed surfaces and wireframes | Faces, edges, vertices and solid topology |
| Textures and UV mapping | Not supported | Not normally included |
| Materials | Limited support | Application dependent |
| Object groups | Layer and entity structure may vary | Body topology is retained where supported |
| Common workflow | Legacy CAD, CAM and surface-modelling tools | OpenCascade and solid-modelling CAD systems |
Choose BREP when
Your next application or supplier specifically requires a BREP file.
Solid modelling, topology and CAD kernel workflows is the next stage of the workflow.
The target geometry representation suits the downstream task.
Keep IGES when
Your project still depends on data unique to the source format.
You need to continue editing in Legacy CAD, CAM and surface-modelling tools.
The model is still being prepared rather than handed off.
Before continuing
Check the converted
BREP before the next step
Changing the file format does not automatically make a model production-ready. Review these checks in the application used for your next workflow.
Important: File formats may not include a standard unit definition. Always verify dimensions after conversion.
- 01
Verify dimensions and scale
Confirm that the converted BREP file uses the expected size and unit interpretation.
- 02
Inspect the complete geometry
Check that all expected bodies, surfaces, curves or drawing entities are present.
- 03
Review surface orientation
Look for flipped faces, inconsistent normals or reversed boundaries after conversion.
- 04
Check topology and open edges
Inspect gaps, overlaps, invalid edges and disconnected geometry before downstream use.
- 05
Confirm layers and object structure
Verify that supported layers, groups and model organisation were translated as expected.
- 06
Open the file in its target application
Preview the BREP result in the software used for the next workflow before production use.
Common problems
IGES-to-BREP conversion troubleshooting
Most conversion issues come from differences between file formats or problems already present in the source geometry.
The BREP file has the wrong size
The source and destination tools may interpret units differently. Open the BREP file and select the correct unit or scale.
Fix: Verify units and dimensionsTextures or materials disappeared
This can be expected when BREP does not support the texture, UV or material information stored by IGES.
Fix: Keep the original IGES visual dataThe model has missing faces
The IGES source may contain open edges, invalid polygons, overlapping geometry or inverted normals that remain visible after conversion.
Fix: Inspect and repair the source geometryThe conversion fails on a large file
High polygon counts and complex geometry need more processing. Confirm the file is below 300 MB and opens correctly in a viewer.
Fix: Simplify unnecessary geometry detailSecure processing
Your 3D files remain yours
Product models can contain confidential engineering information. Privacy and file handling stay explicit beside the tool.
Encrypted upload
Files are transferred through a secure connection.
Automatic deletion
Uploaded and converted files are deleted after 7 days.
You retain ownership
Conversion does not transfer ownership of your model.
Not publicly listed
Your uploaded files are not added to the Marathon CAD library.
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Frequently asked questions
Everything to know before converting
Quick answers about formats, pricing, file limits, conversion quality and privacy.
How do I convert IGES to BREP online?
Upload your IGES file (.igs or .iges) to Marathon OS, choose BREP as the output format, and download the converted file in seconds — no software installation required.
Why convert IGES to BREP?
Converting IGES to BREP helps you move CAD data between tools, suppliers, and workflows without installing desktop software. Marathon OS handles the conversion in the cloud so you can download a BREP file in seconds.
What IGES and BREP file extensions are supported?
This converter accepts .igs or .iges input files and outputs .brp or .brep. Upload up to 300 MB per file.
Is the IGES to BREP 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 7 days.
Do I need any special software or training?
No — upload your IGES file and download BREP directly in your browser. No plugins or desktop CAD tools required.
Can I convert large IGES models to BREP?
Yes — Marathon OS is optimized for large and complex CAD models. You can upload files up to 300 MB for IGES to BREP conversion.
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