What the BREP keeps
- Exact curves and surfaces
- B-rep solids as solids, trimmed surfaces as surfaces
- Every part in its assembled position
- Coordinates in millimetres, with inch files scaled
Convert IGES or IGS to BREP online
Upload an .iges or .igs file and download an Open CASCADE BREP file with the exact geometry, ready for FreeCAD, CadQuery, gmsh or your own OCCT code. First 2 files free, any size up to 300 MB. After that, 1 credit per file.
IGES to BREP converter
Exact · Open CASCADEIGES
From IGES.iges or .igs
BREP
exact · Open CASCADE
Sign in with Google or an emailed code to upload your own file. The sample file works without signing in.
Drop your IGES file here
or browse files
.iges or .igs · up to 300 MBFirst 2 conversions free — any size up to 300 MB. Then $2.99 or 1 credit per file, charged at download. Prices include tax.
Have a BREP file? You can also turn BREP files into IGES.
- Files up to 300 MB
- Exact geometry, no triangles
- Native Open CASCADE format
IGES to BREP converter at a glance
- Converts
- IGES and IGS (solids and trimmed surfaces) to BREP.
- You get
- One BREP file in Open CASCADE's native format: the exact shape read from your IGES, coordinates in millimetres. One shape, with no names or colours.
- File size
- Up to 300 MB. We email you when the file is ready.
- Price
- First 2 files free, any size up to 300 MB. After that, 1 credit per file.
How to convert IGES to BREP
IGES to BREP in four steps
To convert IGES or IGS to BREP, sign in, upload your .iges or .igs file above and download the BREP file. The geometry stays exact, with no triangles, and tools built on Open CASCADE load it without translating the IGES again. IGS to BREP works the same way.
Upload
Sign in, then drop a .iges or .igs file up to 300 MB onto the converter.
Convert
The exact shape is written in Open CASCADE's native BREP format.
Download
We email you when the BREP is ready. Download one BREP file.
Load
Open it in FreeCAD, CadQuery or gmsh and check the shape.
IGES vs BREP
What changes when IGES becomes BREP
Both formats store exact geometry. BREP keeps only the shape.
What it leaves behind
- Part names, colours and layers
- Any assembly structure (one compound shape)
- Annotations and drawing entities
- The unit label (BREP has no unit field)
What a BREP file is for
Open CASCADE's own format
BREP is how Open CASCADE stores a shape, so OCCT-based tools load it directly.
BREPExact, not meshed
BREP stores the boundary representation Open CASCADE builds when it reads your IGES: surfaces, edges and vertices, no triangles.
IGESSolids or surfaces, as read
B-rep solids in the IGES are solids in the BREP. Trimmed surfaces stay loose faces: we don't sew or heal them.
BREPOne shape, millimetres inside
An assembly comes out as one compound shape with every part in place. A BREP file has no unit field; the coordinates are millimetres.
Most commercial CAD programs don't import Open CASCADE .brep files. To send the model to SolidWorks, Fusion or CATIA users, convert IGES to STEP instead. For meshing, gmsh opens .brep directly, so you can mesh the exact geometry for FEA.
Choose the right format
IGES vs BREP
Pick by what the next program needs.
| IGES | BREP | |
|---|---|---|
| Standard | IGES 5.3, last updated in 1996 | Open CASCADE's native format |
| Geometry | Exact curves and surfaces; solids in B-rep mode | Exact solids and surfaces |
| Units | Stored | Not stored (ours is mm) |
| Names, colours and layers | Possible | No |
| Opens in | Most CAD and CAM programs | FreeCAD, CadQuery, gmsh, Salome and other OCCT tools |
| Best for | CAM and older CAD | Scripts, meshing and OCCT pipelines |
BREPConvert to BREP when
STEPChoose STEP whenThe model is going into FreeCAD, CadQuery, build123d, gmsh or your own Open CASCADE code.
You're in the right placeThe model is going to another CAD program or a supplier.
IGES to STEP for CAD STLChoose STL whenYou need a mesh for printing rather than exact geometry.
IGES to STL for printingOpen it anywhere
Where BREP files open
Any tool built on Open CASCADE reads BREP.
FreeCADOpens BREP
CadQueryimportBrep
build123dimport_brep
gmshOpens BREP
SalomeImports BREP
OCCTBRepTools::Read
In Python, CadQuery's importBrep and build123d's import_brep load the file in one line. In C++, BRepTools::Read does the same.
FAQ
IGES to BREP questions
The format, solids or surfaces, units, meshing, pricing and your files.
Contact usLast updated 6 November 2026What is a BREP file?
A .brep (or .brp) file is Open CASCADE's native format for a boundary representation: the exact surfaces, edges and vertices of a shape. FreeCAD, CadQuery, gmsh and other tools built on Open CASCADE read it.
How do I convert an IGES file to BREP?
Upload your .iges or .igs file to the converter at the top of this page and download one BREP file with the exact geometry. FreeCAD, which is free, can also open an IGES and export BREP. Marathon OS is the paid route: first 2 files free, then 1 credit per file.
Is the Marathon OS IGES to BREP converter free?
First 2 files free, any size up to 300 MB. After that, 1 credit per file. Credit packs bring it down to $1.80 per file. Prices include tax, you pay only when you click Download and credits never expire.
Can I convert IGS to BREP?
Yes. .igs is the short extension for IGES; both convert the same way.
Does IGES to BREP lose geometry?
No. Curves and surfaces stay exact; nothing is meshed. BREP drops what's around the geometry: part names, colours, layers and any assembly structure.
Will the BREP be a solid?
If the IGES holds B-rep solids (type 186), the BREP holds solids. If it holds trimmed surfaces (type 144), the BREP holds the same loose faces: we don't sew them.
What units does the BREP use?
BREP has no unit field. The coordinates are millimetres. We read the unit stored in the IGES, so an inch file comes out at the right size.
Can SolidWorks or Fusion open a BREP file?
Most commercial CAD programs don't import Open CASCADE .brep files. Convert IGES to STEP for them instead.
Can I mesh the BREP for FEA?
Yes. gmsh and Salome open .brep files directly, so you can mesh the exact geometry.
Is .brp the same as .brep?
Yes. Both extensions are used for the same Open CASCADE format.
Do I get a quality report?
Yes. Every conversion comes with a free quality report with 11 checks, including a valid B-rep, the number of solids, a face count match with the IGES, a bounding-box match and whether surface types are preserved.
Can I convert BREP back to IGES?
Yes. Our BREP to IGES conversion keeps the geometry exact.
Which IGES files can I upload?
IGES files from any CAD program, as .iges or .igs, up to 300 MB. We read both solids (type 186) and trimmed surfaces (type 144). Files that use commas as decimal points, which some SolidWorks setups write, are fixed before reading.
Do I need an account?
To upload your own file, sign in with Google or an emailed code. The sample file works without signing in.
How long does an IGES to BREP conversion take?
It depends on the file. Large assemblies can take a while, and we email you when the file is ready.
Are my IGES files private?
Uploads and downloads use HTTPS. Uploaded and converted files are deleted automatically after 7 days, and converted files aren't added to the public CAD library unless you publish them. You keep ownership of your design. See the Privacy Policy.
Convert your IGES file to BREP
An exact Open CASCADE BREP, ready for FreeCAD, CadQuery and gmsh. First 2 files free, any size up to 300 MB. After that, 1 credit per file.
Pricing
Pay as you go, cheaper by the pack
Your first 2 CAD file conversions are free, any size up to 300 MB, including the download. From conversion 3 on, each file costs 1 credit or a one-time payment, charged only when you click Download. 1 credit downloads any file up to 300 MB, and credits never expire.
Starter
3credits
$7.99
$2.66 each
3 downloads of any size. Good for a one-off project.
Pro
5credits
$12.99
$2.60 each
5 downloads of any size. The everyday choice.
Team
10credits
$19.99
$2.00 each
10 downloads of any size. Best balance of price and volume.
Studio
15credits
$26.99
$1.80 each
15 downloads of any size. Lowest price per file.
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